I enjoyed my stay in this apartment. The communication with the owners was excellent, there were no problems.
The apartment is clean, well maintained with excellent design.
Of the minuses: it was cold in the apartment and in my opinion the price is too high for such a small room, but this is more of a Berlin's problem in general, and not this particular apartment.
I can definitely recommend it if you are alone and need to stay for a short period of time.