With minimal correction:

The course I want to take is Miss Wang’s badminton course. She was an athlete. She retired from the national badminton team and now she is my college teacher. I have been in her class before. I think she is the best badminton teacher in my college. But unfortunately, she is not eligible to launch a course because of new rules which say that teachers who want to launch courses should have their own published papers. Miss Wang focuses on real sports; so, she doesn’t have her own paper. I want to take her course because she has a great training method which helps us improve. She has advanced and professional theories. We can improve our skills after learning from her.

With additional suggested edits:

The course I would like to take is Miss Wang’s badminton course. Miss Wang was an athlete who retired from the national badminton team and is now my college teacher. I have been in her class and I think she is the best badminton teacher in my school. Unfortunately, however, she is no longer eligible to convene a course because of a new set of rules, which states that teachers who want to convene a course need to have published a paper. Miss Wang has always prioritised practice over theory; so, she has yet to publish an academic paper. I want to take her course because she has a great training method, which I believe is capable of helping me improve. Despite not having published her own paper, Miss Wang’s theoretical understanding is solid – and she is very capable at applying theories to practice. I’m confident that I will be able to improve my skills under her guidance.

Note: There is a contradiction in the paragraph. You said: Ms Wang is not eligible to launch a course. But she has a course (which you wish to take). So, this needs to be clarified.

Aside from this, your English is very good. Well done.