When I create a camera and press Numpad 0 then is shows me always inside the "Planetsurface" and this however I place it, I don't understand why and how to change this ...
Thank you by advance!
Sounds like you might have multiple cameras in your scene. Check your outliner to make sure there is only one camera, and if there are extras, delete them.
If there is only one camera, then remember that all objects are added at the 3D cursor, which is likely inside of your Planet Surface object. You can always hide the Planet Surface object and move the camera out.
Hopefully that solves your issue! If not, we can search for more solutions.