Hi I am student from Nepal.I already finished my three months chinese language course in shanghai.

i studied in shanghai maritime university , donming road and before coming to shanghai the Chinese embassy in Nepal Give me 4 mths visa ..after complition my course right now as a part of internship i have been hired by a company in shanghai, but it going to finish in 31 st Of july so is there any chance that i can extend my upto 2 mths by myself because after course completion college provide me i month visa..or can i change student one into working one ..i am in trouble can you help me?