With my Asian students I faced a lot of challenges with learning Russian pronunciation. It`s really difficult to pronunce correctly Р, Л, М sounds for them due to the different articulation background.
I would like to share with you a tip I found for R sound.
Russian r's are formed by flapping the tip of your tongue against the alveolar ridge (behind your upper teeth)-you only need to flap once or twice. A good way to learn how to do this is to say the word рука only give a really strong puff of air as you say the р.