diff --git a/api/src/main/java/org/densy/polyglot/api/util/LanguageMappingBuilder.java b/api/src/main/java/org/densy/polyglot/api/util/LanguageMappingBuilder.java
index 47aeb92..6e94d4a 100644
--- a/api/src/main/java/org/densy/polyglot/api/util/LanguageMappingBuilder.java
+++ b/api/src/main/java/org/densy/polyglot/api/util/LanguageMappingBuilder.java
@@ -5,15 +5,30 @@
 import java.util.HashMap;
 import java.util.Map;
 
+/**
+ * Language mapping strategy builder.
+ */
 public final class LanguageMappingBuilder {
 
     private final Map<Language, Language> mappings = new HashMap<>();
 
+    /**
+     * Sets the fallback language for a missing language.
+     *
+     * @param missingLanguage missing language
+     * @param mappedLanguage  fallback language
+     * @return the builder itself
+     */
     public LanguageMappingBuilder put(Language missingLanguage, Language mappedLanguage) {
         this.mappings.put(missingLanguage, mappedLanguage);
         return this;
     }
 
+    /**
+     * Builds language strategy.
+     *
+     * @return LanguageStrategy
+     */
     public LanguageStrategy build() {
         return LanguageStrategy.mappingsOf(mappings);
     }
diff --git a/core/src/main/java/org/densy/polyglot/core/language/BaseLanguage.java b/core/src/main/java/org/densy/polyglot/core/language/BaseLanguage.java
index 4855531..0780bf0 100644
--- a/core/src/main/java/org/densy/polyglot/core/language/BaseLanguage.java
+++ b/core/src/main/java/org/densy/polyglot/core/language/BaseLanguage.java
@@ -80,7 +80,7 @@ public static BaseLanguage parseLanguage(String languageCode) {
     public static BaseLanguage parseLocale(Locale locale) {
         Objects.requireNonNull(locale, "locale must not be null");
 
-        String language = locale.getISO3Country();
+        String language = locale.getLanguage();
         String country = locale.getCountry();
 
         if (language.isEmpty() && country.isEmpty()) {
diff --git a/core/src/main/java/org/densy/polyglot/core/provider/JsonFileProvider.java b/core/src/main/java/org/densy/polyglot/core/provider/JsonFileProvider.java
index a462e07..d1fe57f 100644
--- a/core/src/main/java/org/densy/polyglot/core/provider/JsonFileProvider.java
+++ b/core/src/main/java/org/densy/polyglot/core/provider/JsonFileProvider.java
@@ -5,6 +5,7 @@
 import org.densy.polyglot.api.language.Language;
 import org.densy.polyglot.api.language.LanguageStandard;
 import org.densy.polyglot.api.provider.TranslationProvider;
+import org.densy.polyglot.core.util.ProviderUtils;
 
 import java.io.File;
 import java.io.FileReader;
@@ -48,10 +49,10 @@ private void loadTranslationsFromFolder() {
 
                 if (languageStandard.matches(languageString)) {
                     Language language = languageStandard.parseLanguage(languageString);
-                    Map<String, Object> data = gson.fromJson(new FileReader(file), new TypeToken<Map<String, Object>>() {
+                    Map<String, Object> translations = gson.fromJson(new FileReader(file), new TypeToken<Map<String, Object>>() {
                     }.getType());
-                    Map<String, String> flattenedTranslations = flattenMap(data, "");
-                    translations.put(language, flattenedTranslations);
+                    Map<String, String> flattenedTranslations = ProviderUtils.flattenMap(translations, "");
+                    this.translations.put(language, flattenedTranslations);
                 }
             } catch (IOException e) {
                 throw new RuntimeException("Error loading translation file: " + file.getName(), e);
@@ -61,24 +62,6 @@ private void loadTranslationsFromFolder() {
         }
     }
 
-    @SuppressWarnings("unchecked")
-    private Map<String, String> flattenMap(Map<String, Object> map, String prefix) {
-        Map<String, String> flattened = new HashMap<>();
-
-        for (Map.Entry<String, Object> entry : map.entrySet()) {
-            String key = prefix.isEmpty() ? entry.getKey() : prefix + "." + entry.getKey();
-            Object value = entry.getValue();
-
-            if (value instanceof Map) {
-                flattened.putAll(flattenMap((Map<String, Object>) value, key));
-            } else {
-                flattened.put(key, String.valueOf(value));
-            }
-        }
-
-        return flattened;
-    }
-
     @Override
     public Map<Language, Map<String, String>> getTranslations() {
         return new HashMap<>(translations);
diff --git a/core/src/main/java/org/densy/polyglot/core/provider/YamlFileProvider.java b/core/src/main/java/org/densy/polyglot/core/provider/YamlFileProvider.java
index cfe8df4..fd10800 100644
--- a/core/src/main/java/org/densy/polyglot/core/provider/YamlFileProvider.java
+++ b/core/src/main/java/org/densy/polyglot/core/provider/YamlFileProvider.java
@@ -3,6 +3,7 @@
 import org.densy.polyglot.api.language.Language;
 import org.densy.polyglot.api.language.LanguageStandard;
 import org.densy.polyglot.api.provider.TranslationProvider;
+import org.densy.polyglot.core.util.ProviderUtils;
 import org.yaml.snakeyaml.Yaml;
 
 import java.io.File;
@@ -47,9 +48,9 @@ private void loadTranslationsFromFolder() {
 
                 if (languageStandard.matches(languageString)) {
                     Language language = languageStandard.parseLanguage(languageString);
-                    Map<String, Object> data = yaml.load(new FileInputStream(file));
-                    Map<String, String> flattenedTranslations = flattenMap(data, "");
-                    translations.put(language, flattenedTranslations);
+                    Map<String, Object> translations = yaml.load(new FileInputStream(file));
+                    Map<String, String> flattenedTranslations = ProviderUtils.flattenMap(translations, "");
+                    this.translations.put(language, flattenedTranslations);
                 }
             } catch (IOException e) {
                 throw new RuntimeException("Error loading translation file: " + file.getName(), e);
@@ -59,24 +60,6 @@ private void loadTranslationsFromFolder() {
         }
     }
 
-    @SuppressWarnings("unchecked")
-    private Map<String, String> flattenMap(Map<String, Object> map, String prefix) {
-        Map<String, String> flattened = new HashMap<>();
-
-        for (Map.Entry<String, Object> entry : map.entrySet()) {
-            String key = prefix.isEmpty() ? entry.getKey() : prefix + "." + entry.getKey();
-            Object value = entry.getValue();
-
-            if (value instanceof Map) {
-                flattened.putAll(flattenMap((Map<String, Object>) value, key));
-            } else {
-                flattened.put(key, String.valueOf(value));
-            }
-        }
-
-        return flattened;
-    }
-
     @Override
     public Map<Language, Map<String, String>> getTranslations() {
         return new HashMap<>(translations);
diff --git a/core/src/main/java/org/densy/polyglot/core/util/ProviderUtils.java b/core/src/main/java/org/densy/polyglot/core/util/ProviderUtils.java
new file mode 100644
index 0000000..810b82e
--- /dev/null
+++ b/core/src/main/java/org/densy/polyglot/core/util/ProviderUtils.java
@@ -0,0 +1,38 @@
+package org.densy.polyglot.core.util;
+
+import lombok.experimental.UtilityClass;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * General provider utility.
+ */
+@UtilityClass
+public class ProviderUtils {
+
+    /**
+     * Flattens a nested map into a single-level map.
+     *
+     * @param map source map
+     * @param prefix key prefix
+     * @return flattened map
+     */
+    @SuppressWarnings("unchecked")
+    public Map<String, String> flattenMap(Map<String, Object> map, String prefix) {
+        Map<String, String> flattened = new HashMap<>();
+
+        for (Map.Entry<String, Object> entry : map.entrySet()) {
+            String key = prefix.isEmpty() ? entry.getKey() : prefix + "." + entry.getKey();
+            Object value = entry.getValue();
+
+            if (value instanceof Map) {
+                flattened.putAll(flattenMap((Map<String, Object>) value, key));
+            } else {
+                flattened.put(key, String.valueOf(value));
+            }
+        }
+
+        return flattened;
+    }
+}