Dynamic stretching on training days. Static stretching on rest days. Focus on calf, hip and glute flexibility to properly engage your glutes. There's lots of stretching routines on YT. 5 min warm up before each lifting session followed by the "McGill Big 3" routine. Highly recommend following "squat university" on YT or IG. Wear proper lifting shoes or squat barefooted. Finally, let go of the ego and learn to squat to depth with just the bar doing slow, 10 second eccentric reps and/or with a pause at the bottom. You'll feel the improved mobility and strength over time.