I am a novice lifter myself, so I would defer to the likes of Glenn, Greg, Yoon, and Brian on this. First, good work. Moving it nicely and with crispness, so you're doing well with that weight - what is it, 175lbs?
But a few things jumped out at me from the start.
First, nomenclature - 1st pull, floor to above the knees. 2nd pull, above the knees to full extension (ie body is completely erect, shoulders are shrugged - some call it triple extension (knees, hips, and shoulders - some include ankles (on toes). 3rd pull, you get your ass under the bar.
1. Shoes? Lifting shoes are optimal, running shoes suck, chucks are better. Personal preference, but I would like to see you wearing something with a solid sole.
2. Your start position is a bit off - your lower back is still rounded when you start the movement. You really need to shoe horn yourself into that first pull and think "drive my feet through the floor" or "extend my knees." That is the first pull.
3. That start position also points out another flaw I see. Your shoulders are never in front of the bar. You need to think about really getting your shoulders and head in front of the bar so you can use your entire upper body as a lever when you explode at the top of the second pull. You need to think head and shoulders in front of the bar and actively pushing the bar back towards your body by flexing your lats and cocking your wrists "under."
4. you seem to be bumping the weight forward with your quads instead of brushing the thighs. The bar path should be somewhat straight from the floor. As a result, you should not step forward with each successive rep. You ended up about 18" in front of where you started.
now, this is a lot. I say work on one thing at at time. I would say start with really getting your shoulders in front of the bar and using your lats to keep the bar close to your body. Think push the bar back with my lats and keep my shoulders in front of the bar until the bar touches my mid thigh.
I would start with that and work forward from there. But again, I would defer to Glenn, Greg, Yoon, and Brian on this.
All the best,
Lifting heavy stuff is fun and relative......