Judo

The first lesson is how to hit the ground without it hurting

Try a class first; staying on means a gi and a membership. The first months go mostly into breakfalls, learning how to land after being thrown, and nothing else is teachable until that is in place. The heart of it is the instant you find your partner's balance through their lapels, and timing lets a small person throw a large one. Fingers and shoulders take the most damage.