Location is very good, Tramway (M2) to Alexanderplatz is just 1 min walking from the appartment and Subway (U2) is just 5 min away from the building.
The apartment was clean and the oriental room very nice and warm, which we appreciated as it was snowing.
We unfortunately didn't meet the people we expected (the couple: Luca and his wife) but Matt, one of their friends. He was really kind and professional and gave us good advices.
Overall, everything was quite ok except of the noise. The room is at the entrance of the apartment and people started to come and leave from 7am. There was also the boiler in the room which made a surprising noise every nights between 4 and 6 am so our sleep was cut and it wasn't really appreciable. Be aware of this if you want to sleep a bit late in the morning! You should choose another room in the appartment.
Also note that the lift requires a special key that is not provided so you have to use the stairs to reach the 4th floor!
It was our first experience with Airbnb and for sure not the last.