Advice needed

Hi everyone ,i' m emelie
i need some advice about an american visa,i' m in china right now studying chinese and hotel and management  and i will be graduate next year and the problem is my boyfriend live in san francisco he wants me to apply for the visa but i hesitate for many reason because he wants me to ask  for a visa for me to go to U. S and get married there but i m hesitating since he is only a green card holder not a citizen and i think it s impossible even if i go i have to come back after 30 days i think cuz he is not a citizen yet  and  i was thinking if he is sending me a contract because he have a company in the U.S is that going to work since he is not  CITIZEN ,can he bring an employee from outside the U.S,IF you guys have any advice everything that can help me any idea because i want to start to apply my visa soon ...
thanks a lot

thanks for replying i am contacting you right now ,but it' s not open