Girls, what should we do so that the baby turns over on his tummy by h…

Girls, what should we do so that the baby turns over on his tummy by himself? We do gymnastics, charging, massage, and fitness ball every day. On the floor from 3 months. I show how to turn over correctly but he doesn't want to go in any direction. He can turn well on his side, but he doesn't want to go on his belly.