I suggest you practice your left and right maneuvering to ensure your safe behind the barriers. Then start shooting the column to the far right first. When a shot comes at you - quick move to a location and shoot what you then get back to that far right column and complete. Then move the far left column, since it should be moving that direction. Basically work the sides then the lower rows (not columns) in the middle and that should help you. Good Luck!