The mobile app has an own language setting. It can follow the account language, but doesn't have to. Looks like you have to change the setting in the app.

I done that but it did not worked

did not worked

Sounds like your account may be compromised. Follow directions in the following thread:
https://steamhost.cn/steamcommunity_com/discussions/forum/1/601910394159787624/#c601910394159787702

I don't got any malware but this has happened before and it changed Bach after a day or so and now it is just staying like that

Originally posted by matousfabik8:

I don't got any malware but this has happened before and it changed Bach after a day or so and now it is just staying like that

I would still go through the steps. The most common method accounts are compromised is through fishing where no malware or viruses are involved, just social engineering.

Yup, better safe than sorry, also its the most likely cause in general, for anything language related suddenly changing.

Wth I just deautorized the all accounts from mobile and the language is back to normal

The implications are alarming to say the least. Hopefully you can figure out how your account was compromised so as not to find yourself in this situation in future. Steam will not reimburse stolen items or wallet funds nor reverse game and VAC bans.