I've just figured out how to achieve the German R sound. The tongue needs to be pushed down to the base of your mouth.
Press your tongue against your lower gum to find the right level. Now stop pressing your tongue against your lower gum but do not let your tongue come up again and it should be in the right position.
Press your tongue against your lower gum to find the right level. Now stop pressing your tongue against your lower gum but do not let your tongue come up again and it should be in the right position.