The save file can retain language flags.

A very common issue, especially among players who bought cheap keys online, is ending up with a region-locked version of the game, specifically the Russian one. These keys are often significantly cheaper but come with major language restrictions. Many players have reported that these versions are locked to Russian and, while you might be able to change the text and subtitles, the audio remains permanently in Russian.

Your version may be region-locked. This is common for copies of the game purchased in certain regions. You may need to either use your Steam properties to change the language (which will force a download) or look for a community-made unlocker or patch to add the missing language files back into your game.

Choose your preferred language and launch the game. You may be prompted to install a specific update containing the new language files.

You likely mixed versions (e.g., a v1.10 language pack with a v1.04 game patch). You have two options:

Кликните по кнопке «SETTINGS» в правом нижнем углу (либо нажмите F3): В открывшемся экране нажмите на «GENERAL» (слева посередине) Steam Community

The Steam version is the most flexible. The Epic Games version sometimes fails to trigger voice-over downloads.

The Ultimate Guide to Far Cry 4 Language Packs: How to Change Audio and Text Languages

Under the section, locate the Language dropdown menu. Select your preferred language.