i met a girl few month ago,d relationship was meant to be a game but suprisingly we both became too commited.the girl is engaged to another man which i know initially but never care to know the level of the engagement.now we are madly in luv but the girl is telling me that she didnt think that our relationship will lead to marriage cos her parent has known the other guy.now i told the girl i want to quit but each time shes refusing, pls advice me i dont have any other girl

If she's engaged as you said, then it would be best for you to let go and look for another girl. There are millions of single girls out there; make your choice and live a happy life with her.