What few writers understand before visting a set is just how boring they are. For my money, a writer’s time is better spent in the editing room.
Ratio of pages to screen time
A page-a-minute is a good rule, with exceptions.
How much research does it take?
You don’t need to know everything, just enough to firmly place your characters in the world.
What should a 14-year old do?
There’s so much to play with, study and write about in the world around you. Start there.