I am a non EU citizen. I am applying for a Blue card in France but the location I want to live in is in Germany Berlin.
How does that apply in my case, working for a certain EU country and living in an other? Which country issues the Blue card in this case France of Germany? And if I want to apply after 21 month for permanent residence, whose country rules do i have to follow up?
That's not what the Blue Card system is for. You have to apply and reside in the country where you would be working. Since you mentioned applying in France, let's assume you found a job there. The residence permit you will get does not allow you to live in Germany and won't offer a path to permanent residence there. The only rules that apply are French rules because you are not even supposed to live in Germany.
Under the Blue Card rules, your employer can also send you to Germany for some time and there is a slightly easier path to transition to another Blue Card job in another participating country but those are secondary considerations. The Blue Card is not an EU-wide residence permit and you cannot chose where you live.
