How do I remove the air? When does the cushion get hard and when soft? How and why?

Changing the hardness of the pillow means removing some of the air from it. The special pump sucks out the air and the cushion becomes harder. You can change both the shape and the hardness of the cushion. To do this you can use the special manual or electric pump. After screwing the hose on to the pillow valve, the pillow will soften, and when pumping the pump it will harden. After shaping, you should unscrew the pump and protect the valve with the cap.