how to get better at pvp

i been playing with my friend who was way better then me he could take me on with a saibaman and take me down with goku god or worse but just from playing against him again and again i got good enough i mange sometimes to take the upper hand or even destroy him completely
but he is still kinda better like he adapt faster but i get rusty super fast if i do PvE i forget very fast all my PvP skills how can i keep them sharp and practice to get even better?

what skills and stuff should i learn and train and how can i?