Try immitating a purring cat or a growling dog to get the "rrrr" flowing. That's stronger than an French "r" but that would be a start. To give you a clue, an exagerated "r" would be said mouth open with a big smile and the rolling happens at the very the back of the mouth (you should feel it)

You know, the "r" that you are using in english is quite the same in french

thanks, I have got it.

for the R just think you have a hair stuck in your throat on the top side and you want to get rid of it. Then say a word with an r like carré...