We had a great time in Frank's apartment. Check-in was easy and the apartment is very clean. The neighborhood, Prenzlauer Berg, is a very nice area to stay in Berlin. In front of the door is the U-Bahn and around the corner are nice restaurants and shops.
The apartment is located on the ground floor on a busy road. The building is in a courtyard behind a gate, which feels safe. The apartment is therefore not located directly on the busy road, so you will not be bothered by this. However, the building is a little noisy.
We definitely recommend this apartment!