Gym, legs
The main strength lift for legs. Always use a rack with safety bars.
Phone at hip height, about 3 metres away, filming you from the side.
Your whole body, head to feet, needs to be in the picture. The coach will remind you if it can't see you.
Too shallow
Reach parallel, using a lighter weight if needed.
Chest collapsing
Brace harder and keep your chest up out of the bottom.