How much Detail before starting actual development?

Hello,

I am currently developing a story-driven game for my gamejam. It is a farming-sim like stardew valley or animal crossing but with a focus on narrative and the overall story arc.

In my previous games, I never focused so much on that. That's why I wanted to ask:

How much of the Story, the dialogues, optional quests, etc do you write before the development and how much do you write on the go?