Unable to answer "What is the width of the opening here?" – Gate – https://osm.org/node/736651743 via StreetComplete 62.2:

Dauerhaft für Publikumsverkehr gesperrt. Steinbruch obere Kante

Attached photo(s):
https://streetcomplete.app/p/327577.jpg
https://streetcomplete.app/p/327578.jpg