Nikolai's place is comfortable & clean. We did not get to meet Nikolai but her friend managed to welcome & show us the house when we arrived. We had missed our flights so we had to re-arrange our travel plan, Nikolai quickly responded to our message which helped us proceed with the booking.
The location is very central with Metro access. The cafe right below the building is worth visiting as well.

We would highly recommend Nikolai's place if you are in Berlin.