Ответьте на 3 вопроса
What benefits and harms of a professional sport are ?
What kind of sport you are fond of ?
What you prefer whether to take part in the competitions or to watch them ?

The benefits are that you can become stronger and more energetic.  Also good professional sportsmen earn a lot of money.  The harms are that your health can become worse as a result of much strenuous exercise.  Also sport is good for young people.  When you become older, a more practical profession is much better.

I am fond of swimming.

I prefer to take part in the competitions if I am good at this sport.  But as I am not a professional sportsman,  prefer watching them.