I am 22 years old and weight 69 kg. I recently started squatting and deadlifting and upon filming myself and watching the footage I'm pretty sure I have a lot of room to improve. I tried asking some of the coaches at my gym and they say that my form is fine.
The squat is a regular high bar back squat, and I'm using sumo stance for the deadlift.
Also, back squats cause some slight discomfort in the lower back area, I suspect this is also due to my form. Deadlifts feel fine.
Realize that technical proficiency in these lifts takes time...and lots of practice. Also, technique is a very individual thing. I agree with
@Anna C about the full extension at the top of the squat. This means being in a strong tight position. Also, it seems you may be trying too hard to maintain a vertical back as opposed to a flat back. The former causes you to arch way too hard, lose balance and bracing while the latter, while more bent forward, lets your body find the ideal bar path, straight up and down over midfoot. When I started squats, I used to divebomb them, just dropping as fast as possible and praying the rebound would get me back up. It wasn't until, thanks to Pavel, I started focusing on a nice tight descent, like loading a spring and allowing my body to find it's natural path and stack properly. Find your groove, a more controlled descent may help.
As for the deadlift, it looks pretty good, but in addition to Anna's tips, I think you may be shrugging at the top of some reps, using the shoulders to complete them instead of the hips. You basically want to anti shrug through the duration of the deadlift or "make your arms longer". This does a few things when executed properly. It tighten your lats and consequently your midsetion, stops you from trying to pull with your arms, and decreases the total ROM. A drive though of the hips makes the lockout more emphatic and absolute, and doesn't throw the task on smaller muscle groups and make the lift longer. The top should feel like a "static stomp", glutes and legs pressed into the floor and upper torso and abdominals locked.