15u Pitching looking for advice

If you see anything please comment down below!
Any help would be great

The sequencing seems to be bit off at foot strike. Your knee drive knee begins it’s rotation before your throwing arm gets up to 90 degrees. Not getting to 90 is reducing the range of your external rotation. Also your hips and shoulders are rotating together. Additionally, your back has a bit of an arch in it through release. It needs to be chest out to improve your kinetic chain and keep the torque in your rotation. First, try to get to 90 on your arm before you begin to rotate your drive leg. You have good arm speed and intent. If you can get your chain in order you can build some velocity.

Thanks CoachPaul for your advice…is there any video or article you would suggest for me to fix my problem?

Notice how his arm is at 90 when he turns that knee toward the ground. Also notice how the ball stays fixed as he rotates his torso, shoulders, then he gets max ER before the ball slingshot forward? Also, his glove is virtually stationary the entire time the ball is stationary. His back is also reverse C shaped to allow maximum forward flexion at the hips with a table - flat back through release and follow through.