The apartment was exactly as described. We haven't met Steffi and had minimal contact through messaging before and during our stay. She usually answered within minutes. We also had a few misunderstandings, so I will just describe the flat:

Pros:
- The flat is roomy for 4 persons and tight for 6.
- Everything was clean and a lot of utilities are provided in the kitchen and the bathroom).
- You can park your car in the inner courtyard.
- There is a child seat for the kitchen table and a child bed.
- It is a ground floor flat with windows to the street, but the rolling shutters are tight and do their job. The windows are also good quality.
- Nice bakeries a few blocks away with excellent breakfast options.
- Also public transport is good.
- Check in is from 4pm, but you can arrange to leave your luggage in the flat from 11am.

Cons:
- (if you visit Berlin for partying you probably won't care, but if you want to have calm evenings and good sleep...):
- It is a ground level flat, so you will have to keep the rolling shutters down in the afternoons and evenings.
- The street is not too busy, but you can hear almost everything during the hight.
- The walls and doors and the ceiling are pretty thin, so you can hear partying and arriving people from the flat above and from the hallway. Those might wake you up in the night easily.