Vid 1:

I agree with what others have said...shrimping and hips would be good for you to work on. Also posture on your feet. Anytime your shoulders are that far forward from your feet, you are at risk. Your opponent also had poor posture. He was ripe for some over the back grips and related takedowns. I am a big fan of much more aggressive gripping from the start and not giving up the clinch so easily. Good armbar escape and mount reversal! He was also ripe for a sweep when he was defending your choke.

vid 2:
You need to penetrate with your shoot more...watch your neck, keep your head up. You rushed for that armbar from mount before you really had good control of his arm. Be patients, think more about control that about submission. If you control him better, the submission comes much easier :) Nice transition from the armbar attempt to the triangle at the end!

vid 3:
Good sprwal at the start. Nice scampling, good flow in this match!

vid 4:
Again, more drive and penetration on your shoot. You are stopping your movement when you get to the leg. You have to shoot "past" his leg. Think of it like hitting mits. You never stop your punch at the mit, you punch through the mit. Shoots are the same...shoot through the leg, not to the leg.

Overall, nice job for a second time out!