We loved the location of the apartment - we enjoyed the best bits of Kreuzberg and Friedrichshain mostly on foot! There is a U-bahn station at the end of the street as well as a large variety of shops, bars and restaurants! We would recommend Salumeria Lamuri, a delicious Italian deli across the street and Drink Drank, a bottle shop with an amazing selection of beers!
Steffen was very easy to interact with - his studio is in the same complex as the apartment and he is very responsive to texts and phone calls. He was very understanding when we got lost and turned up 30 mins late for check in!
The apartment is as displayed in the pictures - small but functional, the perfect size for a couple. There is a bit of wear and tear but everything is very clean and neat. The bathroom is, as everyone else has said, enormous! And the bed is very comfortable. There is a hairdryer, shampoo and towels provided, though the shampoo bottle didn't have much left in it and we would have been happy with more bath towels for our 5 day stay, but these are minor comments and didn't pose a big issue for us. We had less trouble with the wifi than other reviewers have, though it did cut out from time to time, I had free roaming data so we didn't particularly mind.
I would stay again and recommend this apartment to friends interested in staying specifically in Kreuzberg! Thanks Steffen!