The two most common bunker problems are allowing your club to hit the ball instead of using the sand as a cushion and allowing your spine or stance to tilt back which causes the club to enter the sand too early
One of the most common faults in the swing is taking the club back outside, to fix this many players try to control the clubhead but in the swing it is actually the club handle that controls the clubhead so put a tee in your grip and measure your handle distance from your body through the swing
Practice swinging with your front foot turned out almost to the target which will stop you from shifting your weight to your front foot on the backswing