diff --git a/td/generate/scheme/td_api.tl b/td/generate/scheme/td_api.tl
index d78933ae3..726645df8 100644
--- a/td/generate/scheme/td_api.tl
+++ b/td/generate/scheme/td_api.tl
@@ -1661,7 +1661,7 @@ languagePackStringValue key:string value:string = LanguagePackString;
 //@few_value Value for few objects @many_value Value for many objects @other_value Default value
 languagePackStringPluralized key:string zero_value:string one_value:string two_value:string few_value:string many_value:string other_value:string = LanguagePackString;
 
-//@description A deleted language pack string @key String key
+//@description A deleted language pack string, the value should be taken from a built-in english language pack @key String key
 languagePackStringDeleted key:string = LanguagePackString;
 
 
diff --git a/td/telegram/LanguagePackManager.cpp b/td/telegram/LanguagePackManager.cpp
index 7b7946c6f..024ba14de 100644
--- a/td/telegram/LanguagePackManager.cpp
+++ b/td/telegram/LanguagePackManager.cpp
@@ -66,6 +66,117 @@ void LanguagePackManager::inc_generation() {
   language_pack_version_ = -1;
 }
 
+LanguagePackManager::Language *LanguagePackManager::get_language(const string &language_pack,
+                                                                 const string &language_code) {
+  std::unique_lock<std::mutex> lock(language_packs_mutex_);
+  auto it = language_packs_.find(language_pack);
+  if (it == language_packs_.end()) {
+    return nullptr;
+  }
+  LanguagePack *pack = it->second.get();
+  lock.unlock();
+  return get_language(pack, language_code);
+}
+
+LanguagePackManager::Language *LanguagePackManager::get_language(LanguagePack *language_pack,
+                                                                 const string &language_code) {
+  CHECK(language_pack != nullptr);
+  std::lock_guard<std::mutex> lock(language_pack->mutex_);
+  auto it = language_pack->languages_.find(language_code);
+  if (it == language_pack->languages_.end()) {
+    return nullptr;
+  }
+  return it->second.get();
+}
+
+LanguagePackManager::Language *LanguagePackManager::add_language(const string &language_pack,
+                                                                 const string &language_code) {
+  std::lock_guard<std::mutex> packs_lock(language_packs_mutex_);
+  auto pack_it = language_packs_.find(language_pack);
+  if (pack_it == language_packs_.end()) {
+    pack_it = language_packs_.emplace(language_pack, make_unique<LanguagePack>()).first;
+  }
+  LanguagePack *pack = pack_it->second.get();
+
+  std::lock_guard<std::mutex> languages_lock(pack->mutex_);
+  auto code_it = pack->languages_.find(language_code);
+  if (code_it == pack->languages_.end()) {
+    code_it = pack->languages_.emplace(language_code, make_unique<Language>()).first;
+  }
+  return code_it->second.get();
+}
+
+bool LanguagePackManager::language_has_string_unsafe(Language *language, const string &key) {
+  return language->ordinary_strings_.count(key) != 0 || language->pluralized_strings_.count(key) != 0 ||
+         language->deleted_strings_.count(key) != 0;
+}
+
+bool LanguagePackManager::language_has_strings(Language *language, const vector<string> &keys) {
+  if (language == nullptr) {
+    return false;
+  }
+
+  std::lock_guard<std::mutex> lock(language->mutex_);
+  if (keys.empty()) {
+    return language->version_ != -1;
+  }
+  for (auto &key : keys) {
+    if (!language_has_string_unsafe(language, key)) {
+      return false;
+    }
+  }
+  return true;
+}
+
+td_api::object_ptr<td_api::LanguagePackString> LanguagePackManager::get_language_pack_string_object(
+    const std::pair<string, string> &str) {
+  return td_api::make_object<td_api::languagePackStringValue>(str.first, str.second);
+}
+
+td_api::object_ptr<td_api::LanguagePackString> LanguagePackManager::get_language_pack_string_object(
+    const std::pair<string, PluralizedString> &str) {
+  return td_api::make_object<td_api::languagePackStringPluralized>(
+      str.first, str.second.zero_value_, str.second.one_value_, str.second.two_value_, str.second.few_value_,
+      str.second.many_value_, str.second.other_value_);
+}
+
+td_api::object_ptr<td_api::LanguagePackString> LanguagePackManager::get_language_pack_string_object(const string &str) {
+  return td_api::make_object<td_api::languagePackStringDeleted>(str);
+}
+
+td_api::object_ptr<td_api::languagePackStrings> LanguagePackManager::get_language_pack_strings_object(
+    Language *language, const vector<string> &keys) {
+  CHECK(language != nullptr);
+
+  std::lock_guard<std::mutex> lock(language->mutex_);
+  vector<td_api::object_ptr<td_api::LanguagePackString>> strings;
+  if (keys.empty()) {
+    for (auto &str : language->ordinary_strings_) {
+      strings.push_back(get_language_pack_string_object(str));
+    }
+    for (auto &str : language->pluralized_strings_) {
+      strings.push_back(get_language_pack_string_object(str));
+    }
+  } else {
+    for (auto &key : keys) {
+      auto ordinary_it = language->ordinary_strings_.find(key);
+      if (ordinary_it != language->ordinary_strings_.end()) {
+        strings.push_back(get_language_pack_string_object(*ordinary_it));
+        continue;
+      }
+      auto pluralized_it = language->pluralized_strings_.find(key);
+      if (pluralized_it != language->pluralized_strings_.end()) {
+        strings.push_back(get_language_pack_string_object(*pluralized_it));
+        continue;
+      }
+      LOG_IF(ERROR, language->deleted_strings_.count(key) == 0) << "Have no string for key " << key;
+      strings.push_back(get_language_pack_string_object(key));
+    }
+  }
+
+  return td_api::make_object<td_api::languagePackStrings>(std::move(strings));
+}
+
 void LanguagePackManager::get_languages(Promise<td_api::object_ptr<td_api::languagePack>> promise) {
   auto request_promise = PromiseCreator::lambda([promise = std::move(promise)](Result<NetQueryPtr> r_query) mutable {
     auto r_result = fetch_result<telegram_api::langpack_getLanguages>(std::move(r_query));
@@ -88,17 +199,15 @@ void LanguagePackManager::get_languages(Promise<td_api::object_ptr<td_api::langu
 
 void LanguagePackManager::get_language_pack_strings(string language_code, vector<string> keys,
                                                     Promise<td_api::object_ptr<td_api::languagePackStrings>> promise) {
-  bool is_all = keys.empty();
-  auto result_promise =
-      PromiseCreator::lambda([actor_id = actor_id(this), is_all, promise = std::move(promise)](
-                                 Result<vector<tl_object_ptr<telegram_api::LangPackString>>> r_result) mutable {
-        send_closure(actor_id, &LanguagePackManager::on_get_language_pack_strings, std::move(r_result), is_all,
-                     std::move(promise));
-      });
+  Language *language = get_language(language_pack_, language_code);
+  if (language_has_strings(language, keys)) {
+    return promise.set_value(get_language_pack_strings_object(language, keys));
+  }
 
-  if (is_all) {
+  if (keys.empty()) {
     auto request_promise =
-        PromiseCreator::lambda([promise = std::move(result_promise)](Result<NetQueryPtr> r_query) mutable {
+        PromiseCreator::lambda([actor_id = actor_id(this), language_pack = language_pack_, language_code,
+                                promise = std::move(promise)](Result<NetQueryPtr> r_query) mutable {
           auto r_result = fetch_result<telegram_api::langpack_getLangPack>(std::move(r_query));
           if (r_result.is_error()) {
             return promise.set_error(r_result.move_as_error());
@@ -108,19 +217,26 @@ void LanguagePackManager::get_language_pack_strings(string language_code, vector
           LOG(INFO) << "Receive language pack for language " << result->lang_code_ << " from version "
                     << result->from_version_ << " with version " << result->version_ << " of size "
                     << result->strings_.size();
-          promise.set_value(std::move(result->strings_));
+          LOG_IF(ERROR, result->lang_code_ != language_code)
+              << "Receive strings for " << result->lang_code_ << " instead of " << language_code;
+          LOG_IF(ERROR, result->from_version_ != 0) << "Receive lang pack from version " << result->from_version_;
+          send_closure(actor_id, &LanguagePackManager::on_get_language_pack_strings, std::move(language_pack),
+                       std::move(language_code), result->version_, vector<string>(), std::move(result->strings_),
+                       std::move(promise));
         });
     send_with_promise(G()->net_query_creator().create(create_storer(telegram_api::langpack_getLangPack(language_code))),
                       std::move(request_promise));
   } else {
     auto request_promise =
-        PromiseCreator::lambda([promise = std::move(result_promise)](Result<NetQueryPtr> r_query) mutable {
+        PromiseCreator::lambda([actor_id = actor_id(this), language_pack = language_pack_, language_code, keys,
+                                promise = std::move(promise)](Result<NetQueryPtr> r_query) mutable {
           auto r_result = fetch_result<telegram_api::langpack_getStrings>(std::move(r_query));
           if (r_result.is_error()) {
             return promise.set_error(r_result.move_as_error());
           }
 
-          promise.set_value(r_result.move_as_ok());
+          send_closure(actor_id, &LanguagePackManager::on_get_language_pack_strings, std::move(language_pack),
+                       std::move(language_code), -1, std::move(keys), r_result.move_as_ok(), std::move(promise));
         });
     send_with_promise(G()->net_query_creator().create(
                           create_storer(telegram_api::langpack_getStrings(language_code, std::move(keys)))),
@@ -129,36 +245,57 @@ void LanguagePackManager::get_language_pack_strings(string language_code, vector
 }
 
 void LanguagePackManager::on_get_language_pack_strings(
-    Result<vector<tl_object_ptr<telegram_api::LangPackString>>> r_result, bool ia_all,
+    string language_pack, string language_code, int32 version, vector<string> keys,
+    vector<tl_object_ptr<telegram_api::LangPackString>> results,
     Promise<td_api::object_ptr<td_api::languagePackStrings>> promise) {
-  if (r_result.is_error()) {
-    return promise.set_error(r_result.move_as_error());
-  }
-  auto result =
-      transform(r_result.move_as_ok(), [](const auto &string_ptr) -> tl_object_ptr<td_api::LanguagePackString> {
-        CHECK(string_ptr != nullptr);
-        switch (string_ptr->get_id()) {
+  Language *language = get_language(language_pack, language_code);
+  if (language == nullptr || (language->version_ < version || !keys.empty())) {
+    if (language == nullptr) {
+      language = add_language(language_pack, language_code);
+      CHECK(language != nullptr);
+    }
+    std::lock_guard<std::mutex> lock(language->mutex_);
+    if (language->version_ < version || !keys.empty()) {
+      if (language->version_ < version) {
+        language->version_ = version;
+      }
+      for (auto &result : results) {
+        CHECK(result != nullptr);
+        switch (result->get_id()) {
           case telegram_api::langPackString::ID: {
-            auto str = static_cast<const telegram_api::langPackString *>(string_ptr.get());
-            return make_tl_object<td_api::languagePackStringValue>(str->key_, str->value_);
+            auto str = static_cast<telegram_api::langPackString *>(result.get());
+            language->ordinary_strings_[str->key_] = std::move(str->value_);
+            break;
           }
           case telegram_api::langPackStringPluralized::ID: {
-            auto str = static_cast<const telegram_api::langPackStringPluralized *>(string_ptr.get());
-            return make_tl_object<td_api::languagePackStringPluralized>(str->key_, str->zero_value_, str->one_value_,
-                                                                        str->two_value_, str->few_value_,
-                                                                        str->many_value_, str->other_value_);
+            auto str = static_cast<const telegram_api::langPackStringPluralized *>(result.get());
+            language->pluralized_strings_[str->key_] = PluralizedString{
+                std::move(str->zero_value_), std::move(str->one_value_),  std::move(str->two_value_),
+                std::move(str->few_value_),  std::move(str->many_value_), std::move(str->other_value_)};
+            break;
           }
           case telegram_api::langPackStringDeleted::ID: {
-            auto str = static_cast<const telegram_api::langPackStringDeleted *>(string_ptr.get());
-            return make_tl_object<td_api::languagePackStringDeleted>(str->key_);
+            auto str = static_cast<const telegram_api::langPackStringDeleted *>(result.get());
+            language->deleted_strings_.insert(std::move(str->key_));
+            break;
           }
           default:
             UNREACHABLE();
-            return nullptr;
+            break;
         }
-      });
+      }
+      for (auto &key : keys) {
+        if (!language_has_string_unsafe(language, key)) {
+          LOG(ERROR) << "Doesn't receive key " << key << " from server";
+          language->deleted_strings_.insert(key);
+        }
+      }
 
-  promise.set_value(make_tl_object<td_api::languagePackStrings>(std::move(result)));
+      // TODO save language
+    }
+  }
+
+  promise.set_value(get_language_pack_strings_object(language, keys));
 }
 
 void LanguagePackManager::on_result(NetQueryPtr query) {
@@ -177,4 +314,7 @@ void LanguagePackManager::hangup() {
   stop();
 }
 
+std::mutex LanguagePackManager::language_packs_mutex_;
+std::unordered_map<string, std::unique_ptr<LanguagePackManager::LanguagePack>> LanguagePackManager::language_packs_;
+
 }  // namespace td
diff --git a/td/telegram/LanguagePackManager.h b/td/telegram/LanguagePackManager.h
index e0b6cd4fa..745c15269 100644
--- a/td/telegram/LanguagePackManager.h
+++ b/td/telegram/LanguagePackManager.h
@@ -17,6 +17,11 @@
 #include "td/utils/Container.h"
 #include "td/utils/Status.h"
 
+#include <atomic>
+#include <mutex>
+#include <unordered_map>
+#include <unordered_set>
+
 namespace td {
 
 class LanguagePackManager : public NetQueryCallback {
@@ -36,6 +41,28 @@ class LanguagePackManager : public NetQueryCallback {
                                  Promise<td_api::object_ptr<td_api::languagePackStrings>> promise);
 
  private:
+  struct PluralizedString {
+    string zero_value_;
+    string one_value_;
+    string two_value_;
+    string few_value_;
+    string many_value_;
+    string other_value_;
+  };
+
+  struct Language {
+    std::mutex mutex_;  // TODO RwMutex
+    std::atomic<int32> version_ = -1;
+    std::unordered_map<string, string> ordinary_strings_;
+    std::unordered_map<string, PluralizedString> pluralized_strings_;
+    std::unordered_set<string> deleted_strings_;
+  };
+
+  struct LanguagePack {
+    std::mutex mutex_;
+    std::unordered_map<string, std::unique_ptr<Language>> languages_;
+  };
+
   ActorShared<> parent_;
 
   string language_pack_;
@@ -44,9 +71,30 @@ class LanguagePackManager : public NetQueryCallback {
 
   int32 language_pack_version_ = -1;
 
+  static std::mutex language_packs_mutex_;
+  static std::unordered_map<string, std::unique_ptr<LanguagePack>> language_packs_;
+
+  static Language *get_language(const string &language_pack, const string &language_code);
+  static Language *get_language(LanguagePack *language_pack, const string &language_code);
+
+  static Language *add_language(const string &language_pack, const string &language_code);
+
+  static bool language_has_string_unsafe(Language *language, const string &key);
+  static bool language_has_strings(Language *language, const vector<string> &keys);
+
+  static td_api::object_ptr<td_api::LanguagePackString> get_language_pack_string_object(
+      const std::pair<string, string> &str);
+  static td_api::object_ptr<td_api::LanguagePackString> get_language_pack_string_object(
+      const std::pair<string, PluralizedString> &str);
+  static td_api::object_ptr<td_api::LanguagePackString> get_language_pack_string_object(const string &str);
+
+  static td_api::object_ptr<td_api::languagePackStrings> get_language_pack_strings_object(Language *language,
+                                                                                          const vector<string> &keys);
+
   void inc_generation();
 
-  void on_get_language_pack_strings(Result<vector<tl_object_ptr<telegram_api::LangPackString>>> r_result, bool ia_all,
+  void on_get_language_pack_strings(string language_pack, string language_code, int32 version, vector<string> keys,
+                                    vector<tl_object_ptr<telegram_api::LangPackString>> results,
                                     Promise<td_api::object_ptr<td_api::languagePackStrings>> promise);
 
   void on_result(NetQueryPtr query) override;
diff --git a/tdutils/td/utils/port/RwMutex.h b/tdutils/td/utils/port/RwMutex.h
index eee5f3dcd..2eb97e9bc 100644
--- a/tdutils/td/utils/port/RwMutex.h
+++ b/tdutils/td/utils/port/RwMutex.h
@@ -17,6 +17,7 @@
 #endif
 
 namespace td {
+
 class RwMutex {
  public:
   RwMutex() {