My third year life in high school

[bosun]

Can you help me to express the following sentences more naturallly?

1. One thing that I would like to change in my life is my thrid year life of high school.

2. When I was in the third grade in high school, I always sat at desk to study for a university entrance exam and I did not do any exercise and chat with my friends.

3.I realize that if I had played sports or chatted with my friends, i might have been happer during the last year of my high school and might have gotten a better grade at the university entrace exam.

4. I also think I might have studied less feeling the stress and my life would be different now.

[Soup]

One thing I'd change about my life if I could would (have to) be my last year in/of high school, because I was constantly studying for the university entrance exam; I never got any exercise, nor did I hang out with my friends. I realize now that if I had, I might have been happier and gotten a better grade on the university entrance exam. In looking back, I should have studied less, not just because of the stress, but more so because my life would have been different today.