That is a nice resort! I see why you were considering an import.
I managed to put openstreetmap carto into the background from the layers menu in the viewer. What I see does speak against importing: The trails all/most already there. Even more of them.
The area looks a bit empty in waymarked trails, there are no route relations.
I am not aware of a tool to merge openstreetmap and third party data. I’d do like that: Export each trail as gpx or geojson, load that into the editor, align geometries to what is on the ground including all sources, create a route relation of it, mode, name, operator set.
The OSM account should say on its profile that it is used for organised editing.