Do I need to have W2 form ( right now I don't have any job. I just go to school)? Will my girlfriend get green card too( I am us citizen)? What is the requirement for marriage and how get qualify for apply green card to my girlfriend?

You must be employed. You must be able to provide copy of tax return of the past 3 years with income at least 125% of poverty guidelines. You may use joint sponsor but the person must be your household member only.

If you don't meet the eligibility, why not wait... it's more difficult this day and if you failed on the first time, the second time would even be harder. Your GF should maintain her legal status until you are ready, so you don't have to pay attorney fees, etc.