Frank was as awesome host. He answered the messages quickly even being abroad and busy. We found instructions for everything we needed and setting up in the apartment was easy as plugging an USB stick. Linens and towels included were a nice add-on that allowed us to have a lighter luggage.
The description and pictures were very accurate, and the neighbourhood was perfect - there is a supermarket and a drugstore 50m away and it is close to most of the sightseeing places. This way I didn't need to take Berlin's subway system even once.
It fits 5 people, but important to note that 2 must share the couch - it is very comfortable tough.