This seems to be some vantilation or sewer access cover. It has a ladder going down but is blocked by a metal grate.

via StreetComplete 53.2

Unable to answer "What kind of building is this?" for osm.org/way/336062272 via StreetComplete 53.2:

I'm not sure, but I think this is part of the building number 7.

Unable to answer "What’s the surface here?" for osm.org/way/37426496 via StreetComplete 53.3:

Not sure what this is. It's paved with gravel like rocks sticking out.

Attached photo(s):
https://westnordost.de/p/165658.jpg
https://westnordost.de/p/165659.jpg

Unable to answer "Do these steps have a handrail?" for osm.org/way/1169451502 via StreetComplete 53.3:

This doesn't exist. Please delete. -From street complete.

Unable to answer "This shop has been vacant. What’s here now?" for osm.org/node/485634758 via StreetComplete 53.2:

This whole block (including house numbers 50, 105 and 56) is currently under construction.

Unable to answer "What kind of building is this?" for osm.org/way/336062257 via StreetComplete 53.2:

Wellness and indoor pool building.