Looks like you are doing well, but there's still much to improve. Practice the sitting trot. Relax your legs a bit more and absorb the motion through your back and abdominal. Make sure you keep a deep seat. Don't forget to relax your arms and keep your elbows in. The sitting trot is easier to practice while on a lunge line. That way you can fully concentrate on your balance. Soon you will be on your way to mastering the sitting trot! Personally, I found the sitting trot to be more difficult to learn than the posting trot. Take your time. Good luck!