I have an issue with updating string in the language, that became empty strings and not updated one left.

This is an example which ones, but there's many more:

All I wanted is to leave it empty.

I don't think I really understand what your problem is. Maybe if you could explain it better it would be helpful for us.

Normally when you translate your language and you type something into that textarea box, under it, it would appear a "Save" button.

Or if you just press tab to go to the next textarea box it would save automatically.

Sorry, please could you clarify what you are trying to do, other than the above?