Well am sort of in the same position, except am only 17 but i have come to realise that trying to get your parent to approve to you two being together or even get married can go two ways.
one way is that your parent instantaneously like you partner.
Or they don't like your partner, these all come down to either the first impression or the type of your partner is.
One of the ways which you can get your parent to accept your marriages could be to always say nice and good things about your partner and how perfect he/she is for you also telling them about his/her good qualities, but if they still wouldn't accept it.
Then you might have to use the famous blackmail system and tell your parent that he/she makes you happy, but if they dont approve of him/her it destroys you and he/she is the only persn you want to be with. This way even if your parent don't like him they should accept him cause he/she makes you happy.
Another thing to do (as parents usually like certain characteristics in younger people especially in people that will be related to them like a mother would like for their future daughter in-law probably cook nice for or anythinga mother enjoys doing and would like to make sure that when her son is married to this person the wife to be would be able to take very good care of him closest to the wayshe does or even better likewise for the father and future son-in-law) will if they have anything in common will be to let themspend time together doing the things they like that they have in common. I don't think that trying to make your partner and your parent get along for the moment is a very good idea because that would probably just make the parent see more things they wouldn't like in the partner and so they may dissaprove of your partner more.You should think of the long term effect. and if they accept your parnter maybe only for the fact that he/she makes you happy then as time goes on they will come round most especially when you have kids together.
It is not garanteed that all i said will work for definate because people are different and moreover its only advise and am not a professional counsellor but i do like giving people advises and from what i have heard from friends and other people i give advises to am okat it so you can try other things but i really hope you find your way round this to make you, your partner and your parent happy.