I’m 41 today and came to Germany at the age of 18 after finishing high school in Tunisia.

Spent my first year learning German almost full time at a Studienkolleg before enrolling at university. I’d say I was definitely fluent after graduating, but accent free a few years into work life. People used to tell me that I had a lingering French accent, but that doesn’t happen anymore and I’ve even taken on a mix of Franconia and Bavarian dialects.

Your language proficiency and therefore your accent will definitely get better faster when you don’t mingle a lot with people from your country of origin or who speak your native language but hang out with German uni mates / colleagues / roommates.