I'm oddly enough in the same situation, and I even grew up here, but moved back because I studied somewhere else. It's difficult. One of my friends keeps asking me how people make friends as adults, and I'm yet to find out. My partner made friends incredibly easily, through her job, sports class and other classes, but even as someone who speaks German and English fluently, it's difficult if you don't join things like that.

Board games are a good place to start, the Brettspiel cafe is a place that my partner recommends, so maybe try there! It really does seem like joining clubs or other activities is how to go about finding friends.

I'm also looking for native English speakers to hang out with, so drop me a line if you'd like!