The sound of the German r is something that is thought often as one of the reasons that the language is so ugly. It is formed in the back of the throat and one single time the little thing in your palate vibrates.

The German r

rot red Risiko risk Rose rose Ratte rat

If you find this too difficult don't mind. If you use the r-sound that you are used to, you will be understood as well. This is not a sound that can be misunderstood