Start with the grip. Make sure you have the pads of your fingers on the inside of the rim, not the underside of the flight plate.
Looks to me like you're standing up too straight. Bend the knees and bend over at the waist a bit. That will help get your hips engaged a bit more too, but I wouldn't worry about that as much until you stop turning things over.
Make sure you follow through only after the disc comes out of your hand, and follow through in a slightly upward direction. Try not to pronate much during follow-through until you really get a sense for how it's supposed to feel when the disc comes out of your hand.
You might need to adjust your release angle to account for the stability (or lack thereof) of the disc. That orange disc looks really understable (is it a River?) so you need to release it on quite a bit of hyzer and let it flip up. The others seemed to handle the flat release with the touch of wrist turn much better.
I think it's better to learn with a neutral to slightly stable disc thrown on just a bit of hyzer. Keep the elbow below the shoulder and the wrist below the elbow and focus on coming through smooth with a loose arm. Don't try to muscle it or you'll burn everything over.
I like SW's tip about holding onto the disc as well. It's an underrated tip for getting nose down flights. It sometimes feel like my index and middle finger are actually trying to prevent the disc from leaving my grip. I think that helps pull the nose down during release.