Hey! Thank you for playing :)
As explained in the tutorial, press X when you're next to a diamond shaped sprite. It's a checkpoint. When you die, you spawn back next to the fire camp (this is 100% normal, this is story-related), go back in the tunnel and you'll spawn right back at the checkpoint you activated :)
It also works as save feature. If you want to play more another day, just press "Load" after launching the game!