How do I connect between classes in a script?

Hello Professionals,
I started the Creator Kit: Beginner Code course after experimenting with unity software and got stuck in the last "customization" class.

One of the tasks I was tasked with was to remove one unit from the inventory when the bool true was used.
And in the second task of this task if the player's life is full the potion will not be used and no bool false will be removed.

What should I think of when writing variables and classes?

 

There is a thread dedicated to this tutorial: https://forum.unity.com/threads/new-creator-kit-beginner-code.732398/

 

Thank you