I can see that, but for instance the wall I played at, is a bit curved (concave).That’s not true at all. To keep a wall rally going, you need to make sure the ball always lands at exactly the same depth in front of you, You get even better depth feedback because if you miss your depth target, the next shot will be tougher.
Hitting lower it bounces up higher, and hitting higher bounces back lower. This is not how a ball is landing on a real court.