What is the type of visa i can apply? What all the documents needed to be submitted?

You can apply for a L type for visiting her. She can send you an invitation letter and then you needn't provide the round-trip air tickets and hotel reservation. For the Chinese course, you should apply for a X2 type, I think.

X2 type requires your passport, completed application form, a recent passport photo and the admission letter from the university (both orginal and copy versions are required).