I stayed in Mario's apartment in Friedrichshain for a week over new year. I was travelling with my wife and 2 teenage children and we loved the apartment.
Adam promptly met on time at the apartment to welcome us, he was helpful pointing out the local supermarkets and restaurants that were only a short walk.
During our stay both Mario and Felicitas checked in with us on AirBnB and txt message to ensure all was good. Felicitas even dropped in with a few things leading up to New Years Eve.
The apartment has been refurbished completely on the inside and it was exactly the home in Berlin we wanted. It's located in one of the most famous streets of East Berlin with great access to the Ubahn stations and taxi's passing by out the front door.
The outside of the apartment is old and a little run down but once you get use to its appearance it becomes part of its charm.
We were lucky enough to be there when it snowed and experience NYE in Berlin like a local with lots of fireworks out the front windows/balcony.
When we go back to Berlin we would stay there again.
Regards Rob