Help me

I'm trying to get every achievement in stick war legacy just because it's a game I played since a child, I'm stuck on getting to night 20 on the zombie mode, it's the only achievement I don't yet have, does anyone have any tips for surviving? (My skins are miner - leaf, swordwrath - vampire, archidon - ice thing, spearton - vampire, magikill - undead, giant - savage.)