The new demo comes out tomorrow, and some things have changed since the old demo assuming you're referencing, but- if you're still having trouble, I suggest leveling up and taking your time. Unlike the games that inspire it, there is no punishment for death outside of the mansions (which only take you back to the entrance) and you keep your EXP, so usually if you're struggling a bit, it just takes a little more playing to get through what you're struggling with.