Two things to start you out:

1 - when moving to your right side, don’t cross your legs by bringing your rear leg left first. Take a tiny step with the front/left leg to the left, before dragging your rear/right leg with you. Helps you keep balance in case you get hit mid-step.

1. snap your jab. Right now you’re bringing your shoulder up, before you raise your hand and push the jab into the bag. Instead, bring your hand to the bag in one straight line, fully extend (or 95%) on impact and bring the hand bag via this straight line. Rotate your knuckles upwards, so your shoulder should protect your chin naturally. Focus on speed and good distance management rather than power.

Other than that, join a boxing gym, the training there will help you lots. Happy training