Unable to answer "What’s the surface here?" – on bridge: Foot Path – https://osm.org/way/1199259802 via StreetComplete 63.0:

This 'bridge' is a fallen tree, and should be tagged as such if possible. It is crossable, but requires some measure of balance / agility.

Attached photo(s):
https://streetcomplete.app/p/331385.jpg