The final puzzle for the game is a cryptographic puzzle that's been unsolved for five years now. Folk have done just about everything imaginable to solve the puzzle.
There's definitely something about it that I'm not getting.
In my experience getting healing is super rare and I end up dying eventually.
The keys to getting through noita are getting a fast wand to repel enemies and a wand that can dig through stone quickly. There are spell components with negative mana cost and cast time, stack as many of those with a single projectile type spell and you'll make a blaster that can kill enemies safely. The digging wand will let you skip tough sections, tunnel to areas with good loot, let you return to the "sanctuary" zones to edit your wands (if you haven't gotten the "edit anywhere" perk), and such.
Once you have those, you can make more utility wands that let you fly via recoil and whatever else you need.