Sebastian's apartment is cute! We were surprised by how big and open it felt when we walked in. There's lot of natural light. His upcycled furniture was personal. He had a nice speaker we could use, large TV, more seating than is shown in the photos - all the amenities we needed on a less trafficked side street. There are some other details to be aware of before booking:
The front door is completely clear glass and it faces the bathroom door. Germans are much less private than Americans about nudity, so maybe you don't care, but the bathroom can be very clearly seen from the sidewalk at all hours (there's a street lamp directly outside). For example, if your partner is showering and you open the bathroom door to use the sink, your partner will be on full view for the sidewalk - there's no shower curtain either.
Because there's no shower curtain and the floor isn't angled enough, the whole bathroom flooded every time we took a shower. We had to put a towel under the door to stop the water from also leaking into the foyer, lesson learned on night one! The bathroom is all tile, so it's perfectly sanitary, just a slipping hazard for anyone who's differently abled - the airbnb advertises itself as barrier free on the ground floor for anyone who needs that accessibility. It's also wet for a couple hours, so no socks, drying your feet, etc etc.
Being on the ground floor was easy, except that the "cool ventilated" title was describing open windows, not air conditioning. We stayed during the springtime, so most days were perfectly comfortable. On the warmer days, the "soundproof windows" were no longer soundproof because they were opened... it is a relatively quiet street, so if you're a heavy sleeper you'll be fine. For light sleepers, you'll be able to hear the occasional car or partier as they pass on their way home. There's also a train line across the street, but it's fairly quiet. As far as opening and closing the windows... you'll need to climb up a ladder to get to the ones that are designed for ventilation, which also makes the apartment less accessible to those who are differently abled. During the summer, expect this apartment to be warm to the point of being a little sweaty while you sleep.
For the neighborhood, there are some parks nearby, and restaurants that are pretty casual west berlin vibe. If you go a 4-5 blocks north there are some nicer spots too. Not having any check-out responsibilities was nice.