This is the perfect spot for a stay in Berlin. We stayed for nearly two weeks with our 16-month old. The location can't be beat. It was super easy to navigate around the city (even with a stroller) with the apartment as your home base. The S- and U-Bahn are both only a 3-4 minute walk. There are so many fantastic restaurants nearby and an easy walk to DM, Edeka, Aldi and Rewe. The majority of main attractions in Berlin can be reached by public transit in less than 30 minutes.
The apartment is absolutely fantastic. Tall ceilings and exposed brick. It is bright and sunny with giant windows. That being said, the blinds and curtains made the sleeping quarters dark enough for a good night sleep. I was worried that the blinds in the bedroom with the single bed would be too bright for our toddler so brought travel blackout curtains not realizing how HUGE the windows are. Fortunately we didn't need it as the room was dark enough even with him napping during the day or going to bed early before the sun had set.
The layout does include having to go through the larger bedroom (with king bed) to get to the second room (with twin bed) and full bathroom. This wasn't an issue for us as we were traveling as a family but something to consider perhaps if traveling as a group. There is a guest bath in the living area which was great since the entrance to the full bath was in the second bedroom. The kitchen is fully stocked and easy to cook in.
The room is on the raised first floor and overlooks the courtyard. There is an elevator or a quick flight of stairs. Occasionally there were people congregating in the courtyard that we could hear but A) we had the windows open and B) They were gone by 10:30. You are close to the S-Bahn train line and can hear them from the apartment but we didn't find them to be too loud. If you closed the windows you couldn't hear them at all.
As we were traveling with a toddler, Stefanie provided a pack n' play with mattress and sheets as well as an IKEA high chair. An added bonus was a box full of toys that our son absolutely loved!
Communication with Stefanie was easy and quick. We ran into her in the hallway so it appears she has an office in the building which makes it as close to a hotel-like service without being in a hotel. Check in was seamless.
We would highly recommend a stay with Stefanie in this fantastic AirBnB. We were sad to say goodbye on our last day.