I believe there is a bug with the sign next to the potion pit, as there doesn't seem to be any listed ingredients or ingredient effects whatsoever. Luckily, I didn't need to guess the potion for most of the customers, as your introduction of ingredients along with the requested potions made their intended effects clear enough. However, when I got to the potion licensing customer, I was unable to move forward as I have no idea how to achieve the desired effects. If that single bug hadn't been present, the game would be perfectly fine.
The ominous tones of some of the customers was really quite interesting, and it made me feel like the game could really go somewhere! And besides the spelling mistakes and a little cringe, your dialogue is fine too. Hopefully your next game comes out smooth! Good luck.
Edit: I also have to say that starting in full screen made me almost quit out of the game. I hate games that start in full screen. The lack of a way to get out of fullscreen was also not my style. It's somewhat just a personal preference, but it really diminished the opening ambiance for the game...