Can I marry on M-visa in China? and can I convert it to Q1 without leaving China?

dears, currently I have a Chinese M (30 days), and My girlfriend is a chinese citizen, we want to get marry, is it possible to apply? and after we get married, what should I do? Because I want to stay longer with her here, can I apply for Q1 without leaving? if an agent can do it, normally how much does it cost?