There are some issues with potion making -- if you don't put in all the ingredients at the same screen you can't make the potion ("that comes later" message). So make sure you get all of your ingredients before attempting the potion!
It is luck based, and that wouldn't be a problem if it really was a simulation. The real frustration probably lies with the fact that this is timed and has achievements based on that. It is entirely possible for someone to have to repeat a level just so they can get the time under par, which is kind of unreasonable to ask for, especially when the reason is not that the person is necessarily bad at the game.
 "Medieval Chronicles 4"){kind=icon}
 "Tales of Nebezem: Elemental Link Part 1"){kind=icon}
 "Just Passing"){kind=icon}
 "The Darkside Detective Demo"){kind=icon}
 "Dragon of Ecology"){kind=icon}
 "Sticky Sorcerer"){kind=icon}
 "Sleepy Knight"){kind=icon}
 "Landor Quest 2"){kind=icon}
 "Escape3"){kind=icon}
 "Up Left Out"){kind=icon}
 "Tales of Nebezem: Droid's Quest"){kind=icon}
 "Where Are My Pets?"){kind=icon}
 "Medieval Angel 5 -My Destiny- (Part 1)"){kind=icon}
 "The Man Who Can't Jump"){kind=icon}
 "Krystine and the children in chains"){kind=icon}
 "Toodee and Topdee"){kind=icon}
 "The Grey Rainbow"){kind=icon}
 "The Trader of Stories"){kind=icon}
 "Ultimate Assassin 3: Level Pack"){kind=icon}
Just refresh, thanks.