Android game: Silent Castle

So there's this android game that I've been playing recently. And I've been hooked. You make your character sleep in order to generate money so that you can use it to purchase items that will protect you. You will also need to prevent the monsters in destroying the door of the room that you're in so that they can't catch you.

I've experienced some bugs here and there but it's okay. Currently Night 18 at Survival mode. Got any tips how to beat this level?