I think you can be honest and begin with what you wrote: "I'm not a sportsman, because . . ." What do you think is difficult about sports? What sports do you think are really difficult and why?

You could bring up points like: *There is a lot of practice before you can get somewhat good at a sport *There is a risk of injuries which can ruin your career entirely (bring up examples in different sports here) *I'm not sure but you could bring up that some sports are a bit expensive to engage on. For example ice-hockey or golf, I believe the gear for these cost a fortune. Good luck with your homework! :)

You can mention that being successful at a sport requires talent, physical ability, practice, practice and more practice, which takes time. These are only some of the obstacles to becoming successful.

being successfull in sports mean you are doing it better than the rest of the rival also in sport competition is the case. but for example in math summing up the numbers. if you are able to sum up the letters you are successfull. because in these kind of areas your level is being tested with a such kind of math problems in class may be all of the student can be successfull. but in competition you are being compared with the other copmpetitors.