I'm a beginner gymnast.

I have began gymnastics for since a year ago because I watched Kohei Uchimura, a Japanese professional gymnast he who has won gold medals in the world gymnastics championship for five times, and I would like to be like him. However I found that other gymnasts have started for a been doing it for a longer time and so I couldn't possibly become a professional.
I found it And my future work that I want to do is not kind of sports related.

More natural way of saying what you're trying to say would be rather, "I'm not interested in working in sports."

or, "I'm not interested in working as a gymnast."

So I study English to pass the university exam.

I'm beginner gymnast.

I began gymnastics one year ago because I watched Kohei Uchimura, a Japanese professional gymnast. He won five gold medals in the world gymnastics championship, and I would like to be like him. However, other gymnasts have practiced for a long time and I was not as good as them. Instead of pursuing gymnastics as a job, I study English to pass the university exam. OR instead of being a gymnast, I am studying English to pass the university exam.