Unable to answer "What kind of building is this?" for https://osm.org/way/891114357 via StreetComplete 56.0:

looks like a shed or storage thing, but might be a hut to operate the announcement speakers. theres a few of these scattered around the promenade but this one is larger than the others.

Attached photo(s):
https://westnordost.de/p/192815.jpg