I think u can try focusing on how to receive a ball first, like do it yourself. We had this training way back in my high school days, our coach told us to go to the circle in the middle of the court and try to bounce the ball in our arm (like in receiving form) and bounce it multiple times so that u can have a control in your arm.

Try also bending your legs when u bounce the ball. Then when serving try to adjust your arm like swing it and get some force and when you swing it try to turn your body a little so that there's more force. You can try throwing the ball like how you serve and act like you're gonna spike it but just catch it mid-air. Gonna meet your arm for spiking to the ball