I can handle simple tasks myself; I wanted to try something a bit more challenging, but I guess it's still too early. Thanks for the advice, I'll keep it in mind.

Well, this isn't complicated either. But, as I said before, it's easier to do through the editor. In the Manual, the link to which was provided in the previous post, it's not difficult to understand.
In short, if using scripts, since the topic allows:
- You enable the quest based on a specific event and store the day in a variable;
- On the event-trigger for a new day after a certain period, you set the quest to fail and the necessary condition you want;
- On the trigger for changing the ownership of an object, you add code to execute the quest.
Nothing complicated.