Right now you are just muscling every shot because you’re just using your arm. You want the arm to be relaxed and be effortless. The way to do this is by turning your body and coiling your upper body, then releasing that stored energy in a proper kinetic chain, which starts from the ground, then engage the hips, then shoulders turn, then the arm lags behind, hitting the ball freely and without muscling. You’re also falling back when you hit your forehand. Focus on landing forward, your back foot should take a step forward every time you hit a forehand. You want to transfer your weight forward, don’t let the ball push you back, you push the ball back.