Unable to answer "What’s the house number of this building?" – Apartment Building – https://osm.org/way/232210638 via StreetComplete 57.3:

Nr 8 in Jungnickelstraße 
Nr 11 in Wittestraße

Attached photo(s):
https://westnordost.de/p/212392.jpg
https://westnordost.de/p/212393.jpg