Juan is very straightforward and helpful – having a background in giving tours, he will be glad to help You out in getting familiar with the city.
The apartment is small, but very practical – having everything essential (kitchen, bathroom, 2-beds, wifi, etc) – and clean. If at all, then the only thing i missed, was having a washing machine in the apartment (currently paid option, in basement).
Apartment is located nicely 5min walk distance from metro station, that is well connected to different parts of the city (overall public transport is generally pretty good around the city). About 10-15min walking distance, one can find the beautiful Berlin Zoo, variety of restaurants, good gelato place for sweet tooths and for shopaholics, there are some-what many shops to go to.
If You need a place to crash, for quick visit, then I definitely would recommend Juan's place.