Thank you very much for your information. That's exactly what I expected. I changed the unvisible polylines (on my Edge 705) which existed partially in the map source. (Service roads were defined, Tracks/grade1 were unvisible).
(By the way: I use the maps of Ralf Kleineisel which are the best für me using different types of bicycles - road bike and mountain bike).
And of course I already switched on and off the possibility of more and less details in the card. But either I see too much unwished information like unpaved tracks using my fast road bike or too few information using my mountain bike.
I know that the definition of the types of the roads inside the map file could be changed but this is a little too much effort for me.
I am already lucky that I got the service roads and tracks/grade1 visible since a few weeks now.