@manfred-okunneck
I have the Garmin Zumo XT.
There are 2 different options for the the XT
GPX1.2 (Route, Track, POI)
Using this GPX Type you will only see the VIA Points “Stops” on the Map.
The full route is available based on the Shaping Points but they are not shown on the XT Map.
GPX1.1 (Route, Track, POI) will display both the Via Points and Shaping points on the XT Map.
I have no idea on the Garmin Camper 890 but there are members and Admins on the Forum here that will be able to guide you on the correct GPX types to use for that device.