The key to a bunker shot is to eject the sand from the bunker and have the ball go with the sand
Push shots are caused by a swing that is too shallow and from the inside, many times caused by the body moving in front of the ball during the downswing and causing the club to get stuck behind the body
Focus on your left wrist at the top of the backswing and start of the downswing to get to impact properly, many players have a cupped left wrist which changes the angle of the clubface, this causes an open clubface and results in casting and manipulation during the last portion of the downswing