Can I use my F visa to study in China? Can I get the 30 stay duration of F visa extended to 6 months?

I want to study in Guangzhou at Zhongshan university for 6 months. I am told the deadline to apply for the course has passed and the university cannot prepare the JW202 form even though there is almost 2 months for the course to start..

I also do business in China, and the purpose of my visit is to do work, and take the course as well. I have visited China on a F - Visa before for work.

My question is can I go to China on a F-visa since I have work, and take the 6 month course there as well? The visa I received last time stated I was allowed only 30 days stay on one trip even though the visa was valid for 6 months. Can I get that duration extended to 6 months so I can complete my course as well?

Yours sincerely,
Manny