I'm an expat (immigrant?) in Germany. IME expat circles are a problem in itself. People who cling to them end up leaving much quicker than people who mingle with natives, or mingle with people from other nationalities. Not only you don't make long-term friends in those circles (because people are constantly leaving the country), but there's a lot of negativity and shit talking. You need to at least make an attempt to adapt, and those circles can be a replacement to that.
it mirrors a bit the experience I had in university with foreign students/phd students. Some immigrants are only friends with immigrants from the same country and it was surprising to hear that after spending years (sometimes BSc/Msc/Phd or Work) they are completely unable to say a single word in german, have no german friends etc. Usually very unapproachable und uncomfortable to talk to.
Others with mixed groups of friends were way more approachable, I was surprised by some how well they are able to speak the language after just a few years.
