Just encourage him and advise him about steps to remain healthy so that he don't miss his classes. Also tell him to work harder and ask him to decrease the time for which he plays. Also tell him not to play at all when exams are near. Also tell him to listen to light music for 10 minutes and start his study with a cool mind. Tell him to wake up early in the morning, brush and then study for at least half an hour because early morning is the perfect time to study. Encourage him to practise yoga daily. I hope this may help you and your friend.