There are save and load buttons at the top while you're in the city. If those don't work I would reccomend giving some more details and hoping YumeSphere read your comment
I know how to save and load, I'm talking about deleting my save or doing a new game without closing it/quitting, since for some reason when I do this, all the girls will have the same progress but the day will restart, meaning you'll make progress on the girls without wasting a full day. it doesn't matter, it just feels like cheating