Pull out the motor and check to make sure the Pinion gear is not stripped out. G&G motors are the worst for stripped pinion gears. If it is, try adjusting the motor plate screw on the bottom higher and see if it fixes the grinding.
For the feeding, try pushing up on the mag and see if it feeds, if no, try a different mag. If it does, your mag catch may be worn, or needs to be replaced.(also putting some tape on the backside can help with it)