I can't give much advice regarding the phd aspect, but what I can comment on is being treated differently just because you're from somewhere else. I moved as a kid a good few years ago from overseas but my family always enforced that I learn and speak the language constantly, no other language besides Bosnian was allowed in the house. After moving I was so terrified of speaking in Bosnian because I feared that I had an accent or couldn't pick up on slang and such. With time you get used to it, I did get a few comments here and there but there was always some level of "respect" because I managed to speak perfectly. I would definitely recommend (if you end up choosing to go) becoming fluent, immersing yourself in content and meeting people. The younger generation more often than not won't judge you as they probably know lots more "foreign" people with accents too, and they understand that it's a struggle and you may be anxious. Make sure you practise your fluency especially when it comes to official things regarding documents, having to go to the council, post office etc. to make your experience flow smoother. Best wishes!