Learn German in Berlin? I know that many people here who want to learn French or Spanish do it by moving to France or Spain to work or study there.
Given your qualification you will very likely be able to earn money in Berlin without speaking any German. And everything else won't be a problem either, since you speak English.
Also see here. Sounds a bit weird, since as someone from Poland you won't need any "integration" assistance, but those courses are free, or very cheap, and help you to learn German. And as a citizen of the European Union you are not obliged to anything, so you can leave if you don't like it.
Seconded; move to Germany to learn German, not the reverse.
I spent torturous years studying French in school, had tutors, went to camps, and still spoke embarrassing broken anglo French. One semester living in France (studying Biostatistics, not French) and I'm comfortably fluent.
Note: This is about language learning only. I don't know enough to comment on the other aspects of your decision.
I'm about to get my masters degree in computer science. I've been interested in AI for a few years, studying mathematics and machine learning. I'm pretty sure that I would like to work as machine learning specialist. The question I have for you is: how do I do that?
I live in Szczecin, Poland. It's just 150km from Berlin and I am willing to move there if necessary. My current plan is:
I'm still unsure if I should get phd. I don't know if machine learning jobs are common in private sector, but I think they will be in near future (am I wrong about this?). What do you think?