home appliance repair in Germany

Hi there! What network repair shops are there in Germany , especially in Western Germany?

I once again needed my phone to be repaired (screen was broken), but couldn't find any repair shop with adequate price and client-oriented approach in Köln, notwithstanding the good reviews on Maps, but now I'm in Frankfurt and would like to hear from locals what are the network repair shops that work under franchise, cuz in my opinion, they offer the best value for money (based on my experience in Canada).