Unable to answer "What kind of building is this?" – https://osm.org/way/1236674754 via StreetComplete 58.2:

Is this an appartment building or a camouflaged service building? Behind what normally is a window of an apartment there is a huge stair. Further there is no name at the bell except voor KPN.

Attached photo(s):
https://westnordost.de/p/237990.jpg
https://westnordost.de/p/237991.jpg