I used to date a guy who was like that and honestly it is hard. they will take things you say and turn it around they will accuse you of things you just have to have a lot of patience and understanding. when he/she accuses you of stuff just sit there listen to what they say and most of it wont make sense but they don't get that. eventually they will apologize but it will happen constantly in little episodes.
bi polar is when they switch from one emotion to another in an instant. just pay attention to the little things they do or say to see what mood they are in. that way if something happens it wont be a complete shock to you.
Schizophrenia isn't always bout people hearing voices though some do. it where people lose a grip on reality you just have to be patient and help them through it. i hope this helps the best of luck :)