Can people change and this make relationships better

Could use some more information.
People are not likely to change. You get what you see. Not to say its isn't possible, but when and how, this would have to be up to them. You can't make anyone change.

People do change throughout their lives. But, as has been pointed out, you can't make someone change. And telling you that people do change is not meant to give you false hope, if you're looking for some reassurance. Don't judge a person based on their potential, judge them based on what they are, here and now.

People change all the time. That doesn't mean they want to be in a relationship with you though.

I think it depends on how you want the person to change. People can change their attitude towards something, but they can't change their personalities and probably won't want to change their interests just because someone else wants them to. People don't like to be controlled by others and if you want someone to change completely, it's not likely that the person will be willing to do that.