I changed no settings.
It’s a known bug, just try logging out and logging back in or clear your browser cache and try again, should be back to normal after that
Mine was in Italian (I believe) yesterday, and today in Dutch. ._. Clearing cookies does the trick. But I hate to do that as then I have to re-login to a hundred sites. Hopefully it doesn’t become a daily nuisance! I’ll have to try just logging out and back if that does the trick, though.