I thought the squats looked very good for a beginner. But I think you are attempting a power squat groove with an Olympic squat bar position. There is some lumbar rounding at around parallel, but I think it is due to too much torso incline for a high bar Oly squat. If you sit more upright, your knees will have to travel further over your toes. The knees have to move forward on a high bar squat (the bar has to stay plumb over the feet) ... (same with a front squat)

If you want to power squat, you will have to carry the bar lower on your traps, keep the shins more vertical and reach back with your hips. Flat shoes or barefoot is OK for this style, but if you want to Olympic squat, hitting an upright torso is easier attained with a shoe with some heel on it.