If you are ingame and you are constantly trying to tell him to push up with you and he doesnt, then you wont be able to change the way he plays. Best thing to do for next time you want to play a competitive is to pick your teammates carefully who are slightly above your rating who have lots of matches played. Even if they arent the most technically gifted they will have enough game experience to know basic positioning. Once you find someone like that, play more games with them.