Ở cái câu: Volleyball is a very rewarding sport for us. That's why,  when it was entertaining.

Mình nghĩ nên viết thế này: Volleyball is a very rewarding sport for us. Why? Because it was a hobby in the school days when it was entertaining time.

You probably have a lot of sports at school, right? And that's volleyball - a hobby in me. Volleyball is a very rewarding sport for us. That's why    ,      it was a hobby in the school days when it was entertaining. I used to play volleyball at school, together with my best friends, they played very well. But I'm sure I'm not good at it either. I usually play six times a week. It is a work that keeps us effectively entertained. In my opinion, it is also a sport for better health. It makes me happier every day. Helping us improve our health in a good way. Those things made it impossible for me to forget it, a memory that would never fade away in my mind

Những chỗ mình gạch chân và in đậm là bạn nên bỏ nhé :3