I am 17 years old and in my partners family girls are married quickly but she wants to marry only to me how will I plan my future and my studies in medical will take more time and my partners parents are of other caste what will do for my future?

There is no easy answer. I personally would expect her to wait. If she won't, then you must be prepared to lose her. Only you know how much you are willing to sacrifice for love.
Perhaps a formal engagement, a ring, even a contract with her parents for financial settlement if you break the promise.
What do each set of parents say about this? I presume that your parents are paying for your future education for many years to come. Medical schools have arrangements for married student housing, but you haven't even started undergraduate yet. I think you are too young for even an engagement. She and her family should be able to wait until she is 21 in this modern world of advanced schooling.