In Chinese the tongue is put in similar places as pronounced in English, except that, in pronouncing Chinese r, the tongue is rolled up very strongly, (make the tongue really curly) whereas in pronouncing English r, the tongue is just slightly raised in the mouth, without being rolled up that much.
It is difficult to explain the shape of tongue here, but if that doesn't help, I don't think you would have a lot of trouble in being understood if you use the English r to pronounce the Chinese one.
I am sure native speakers can still figure out that it is "r".
I hope this help!
All the best for your Chinese learning!