American requesting a stay for as much time as possible on a tourist visa

I have a chinese girlfriend and her father owns 2 buisnesses there.
I have a month or two until I would be departing and was wondering what the requirements are to be accepted and the easiest way to go about it.. My girlfriends city is Changsha( firework capitol)her fathers buisness is a label printing company and would like for me to be the middle man between firework companies and us..even thought abot teaching english.I would like to just obtain a tourist L but i am open to any ideas. If you could help it would be more apprieciated than you could imagine!