Anecdata: I started to use English as my main language about 11 years ago, and about 4 years ago I adopted German as my secondary language. I remember I had an

Anecdata: I started to use English as my main language about 11 years ago, and about 4 years ago I adopted German as my secondary language. I remember I had an interview in my native language about 5 years ago, and I was literally struggling with finding the words. I was just stuttering for 20 minutes, until they wanted to test my foreign language knowledge... Another time, I remember I was talking with my parents in my native tongue, and suddenly they asked me why I started to talk in English. I haven't even noticed it, it just become "the language that I speak with everyone". With that said, I think it would come back quick, if I was using it again as my main language for a week or two (I stopped using it when I was well into my 20s)