There is nothing to worry about in this case. If you really want to marry, if the marriage is not fake then there is not going to be any problem. You will get your GC in 6 month thats the maximum period. Once you file the papers you will have 180 days grace period that means if you dont go to school or leave your Job(H1) its ok. Just make sure that you have enough evidence to prove your relation. Like picture, joint property, insurance ete. Other thing do not lie when you go for interview just answer whatever the right things. If you need any help you can write me an email i will be glad to help you with.