Unable to answer "What’s the surface firmness of this track?" – Track / Land-Access Road – https://osm.org/way/1316467937 via StreetComplete 62.1:

War früher einmal Schotter, inzwischen durchwachsen siehe Foto.

Attached photo(s):
https://streetcomplete.app/p/321568.jpg
https://streetcomplete.app/p/321569.jpg