Unable to answer "What kind of building is this?" for https://osm.org/way/891417117 via StreetComplete 56.0:

no signs on it. it's locked up. it looks like a shed or storage hut?  might house electric switches and/or utility meters or  something though. it is a mystery :D

Attached photo(s):
https://westnordost.de/p/192809.jpg