I live in Köpenick, which technically is part of Berlin yet is more regarded as a bit of an outsider. Like Kirkby is to Liverpool, or Croydon to London. We're a good 15-20km from the city central areas.
i speak the lingo myself, essential in these outsider boroughs. But Berlin can be a very english-friendly city in the happening areas like Kreuzberg/nord-Neukölln, Prenzlberg, Fhain, Mitte, Schöneberg. Many english have made the move and get on fine. There's an active WG-market (shared-flat scene).
Rents have sadly shot up like crazy now, tho'...no longer the cheap-rent capital of Germany, it's now more in line with the other big cities. Earnings aren't great unless you're specialised.
The city has changed a lot in the last few years too, many migrations/refugees from Arab/African nations have altered the atmosphere in central areas and on public transport. Berlin has always been known to change rapidly, seems every decade it puts a new face on.
We're at a phase in life where we'll be leaving the city and looking for the quiet life in some saxony village lol But Berlin is deffo still a very interesting place for experience-seekers.