I didnt’understand what to do

It's a fun little game, you could definitely expand from it! I like the graphics, and the enemy folding animation is really fun. It would be nice if you could add some story! Perhaps a dialogue before each battle? It was also hard to tell if I was progressing in the dungeon. Perhaps as the level gets harder and harder, the dungeon itself could change, showing that the player is going deeper? It was a little bit tiring to start the game all over after each loss, so I would suggest to add something like a "save" - when you loose, instead of starting at the very start of the game, yoou start at the level you lost at. I couldn't really find the secret, so I'm not sure how well it was implemented, but the idea sounds fun!