hello i would really like to get better at tennis. so does my friend(really only person i can call and say lets play tennis, okay go go go go im on my way bye) i am better than my friend, i have been teaching him what i know and so has his old private instructor. we both atm can't afford lessons. so we depend on ourselves to get better. i have a hopper of decent balls that we feed each other off of. we have good ground strokes. my serve is decent, my friend is still learning. our volleys are a wreck. we can rally from baseline and mini topspin rally in the service boxes. we want to get better at our matchplay but thats that. what else can we do to get better without having a private instructor? any advice on drills and simulations we should do? suggest any videos we should watch etc? p.s. i also wanna start gaining muscle for tennis. what can i do for that, free weights, arm excercises etc?