String translations problem

Hello,

I found that some time ago like 3 weeks ago~ smt happend with my string translations. On every language, every translation is in Bulgarian language. As you can see on this screen:
https://gyazo.com/de874210771420ff720dd7fe32451c56

Before everything was fine. Translations were in proper languages. I have WordPress backup file and my question is: which file can I just copy to get my old string trlanslations back? I wont import every file, just need to know which file is responsible for string translations.