There are many other people, here or here who are looking for the same option. Google has not yet offered a solution to disable the option while on mobile.
Among the possible solutions posted on the second links is to:
- Go to https://myaccount.google.com/language
- Add all the languages you understand in the list
- Reload whatever youtube page you were on
- Youtube shouldn't translate video titles anymore
Note that you may still have some video titles translated for some time because they were cached by your browser.
Also, if you watch videos in languages you don't understand, they will be translated (unless of course you select all languages).
Another possible solution is to change the language of your device to be the same as the language of the video. But it not practical because you will to keep changing languages.
Until Google decides to provide a proper solution, all the above solutions are hit and miss. They work for some and not others.