There are lots of errors to fix everything. But, I'd like to suggest you to practice the introduction first.
The question is asking your opinion, not experts opinion. So, for the last sentence of the introduction, placing your opinion would be better than experts' opinions. In my opinion, expert's sayings could be placed in bodis to support your opinions.
I would change your introduction in that way.
Believing that people are born with certain skills and talents has a long pedigree.Overtime,by dicovering more about human brain and behaviors,some experts declare that people can gain many skills in different fields such as sport and music by being trained from young age and childhood.
-----> It is common to see some artists being born with innate talents perfrom better than others who have made efforts to be excellent.Therefore, some people assert that children without talents cannot be trained as outstanding musicians or athletes, even if they excercise more than other talented people. However, I strongly believe that anyone can become great in music and sports, if they are taught properly and trained harder.