How you hold your hands at the piano can have a great effect on how well you play.
Resting your hands on the piano edge stops you from being able to play quickly or move your hands efficiently. Bending your wrist too much and having straight fingers is also cumbersome. The best way to hold your hands is with a straight wrist and a gentle curve in your fingers. Pretent you have little kittens or fresh eggs or your favourite pet under your fingers. You don't want to squash them. Lift your palms to give plenty of room for movement.
Sit up tall, no slouching!
When you sit up nice and tall your hands are at a better height to play. You also have better movement over the whole keyboard.
Have your feet balanced on the floor or on a foot stool.
Don't sit too close to the piano. Your knees should just be at the edge of the piano, not right underneath.
Adjust the height of the seat with either cushions or use an adjustable stool. Your arms and elbows should be above the keyboard, not dropping below.