It's a hard game, but once you get the hang of it it becomes really fun to look for the potions you need and explore the level as fast as you can!
I think an information screen on the main menu, or an opening level where mechanics are explained along with the effects of each potion would have really helped lowering the difficulty of the game, because when I started playing, I didn't have an idea of what I was supposed to do. For example, I understood that getting the key ends the level, but only after I reached level 3!
Also, everything feels a bit too fast in my opinion? Like how the text boxes disappear really quickly, I had to get the same potion 2 or 3 times to read its entire description. In the same way I thought the player moved a bit too fast, I had trouble keeping up with the game, and I often wouldn't know why I died (or why I beat the level at the beginning). So I'd suggest slowing the player down a bit, and the speed at which your health decreases (to compensate for the lower movement speed).
I hope that this comment didn't come up as too negative, I really like this game. Great work on it!