Usually, getting stuck in the passage of the game is associated with a violation of the main idea of the game: Celica must become an experienced magician, alchemist, and also have good friendly relations with many characters.
The main mechanics to master are listed in the library. There are also tips there.
For example, if Celica does everything right, then both visits to the lion temple are separated by just a night of sleep.
Also pay attention to the character levels that Celica uses in lessons with Nel (the levels should be green). In general, Celica's Experience should constantly grow.