For Garmin devices there are multiple options to transfer a route. There is not the perfect solution, but every solution has its own pros and cons. The most exact way to transfer a route from Kurviger to a Garmin devices uses Basecamp. If you are confident to use Basecamp, then I'd recommend that, but it works without Basecamp and it works with an Android device, so you don't need to carry a laptop with you.
The typical solution is to either use the Track or the Route. If you are not sure what Route or Track means, have a look here.
Plan a route on Kurviger and export either the Track or the Route, when exporting the Route we recommend to create additional waypoints and select the
Garmin ShapingPoint GPX option. When you are comfortable with these options, it might be interesting for you to also try to export both the Route and Track.
Connect your Garmin via USB to your planning device (PC / Android) or insert the SD-card. Note: for connecting Android devices via USB, have a look here. Copy the GPX file to
Garmin\GPX. Disconnect your Garmin and start it.
When you used the Track: go to Apps, Tracks, and choose Import, select the Track. It's recommended to enable the option to show the Track on the map.
Go to Apps, Route-Planning, press on Import and import the route. Now you can start the navigation.
Another nice option to convert a Kurviger-Route to Garmin is to use this German website.
For Garmin devices, there is also a really nice German instruction from Volker Koch.