Carla & Daniel were great! Arranged us getting our keys and helped us get into the apartment at 1AM when our flight was delayed and we were confused about the instructions (top tip: make sure you follow the instructions messaged to you by Carla & Daniel, not the airbnb page itself!)
The flat was lovely and the area we were in was great - directly outside Neukolln flea market and super close to many wonderful bars and cafes (check out mama bar). The only negative was that there were extensive renovations taking place in the building, which meant that building noise started at 7AM every single weekday we were there. Luckily the noise tended to die off around 9/10AM, allowing us to catch up on sleep, but if you're a light sleeper or have a tight schedule, I would recommend checking in about the building works. Apart from that, we had a perfect stay.