Hello, thank you!
I have added mtb:type=allmountain to the 5 "crosscountry" and =downhill to the 4 in the bike park. 
There is one path that is accessible on foot in the bike park, it snakes a bit around the bike track. I uploaded it as https://www.openstreetmap.org/way/1429227131#map=17/44.789825/6.944162

I think it is a bit weird the bike park tracks are now rendered as a "bicicle path" on OSM Carto, but that's a fault of OSM Carto, on OSMAND they still show as a path (black dashes) while a proper bike path is blue long dashes...