Hello from California USA, your friend need to learn how to slow speed maneuvers. He will hurt himself if he does not learn it quickly. He is not ready for that kind of turns. I know what he did, grabbed the front brake. and he did not have power on the rear wheel. Need to learn how to use clutch and throttle control with rear brake. He is not a very skillful rider. Just trying to help and at the same time save a life. Tell him to watch in youtube called "be the boss of your mtotorcycle", by robert simmons.