Ilona showed up in person and showed us how everything worked.
The apartment is in what we interpreted as an old DDR-apartment building. It however seems to be have been refurbished recently, and it is clean and very well kept. We found all necessities, including kitchen stove, fridge and freezer. The beds were good and comfortable. There was a supermarket open 24/7 just a few hundred meters away. The nearest subway station is even closer to the apartment. The WIFI was however somewhat erratic, especially when all three of us were using it at the same time.
Otherwise there was absolutely nothing to complain about, and the place can very much be recommended.