How to write documentation of a project

Hello,

This is more of a general query. I was wondering how a big project is being handled in respect of documentation.
I saw some GDD or game pitch idea but I was more concerned about the internal structure of project. How a big project should be documented so that it is easy for all to work in that project.

Thanks!

for my workflow, currently still working alone but plan to work with more people in the future.

For asset like texture, inside it folder, i add a notepad that include the colour code, source of images/ref , brush type etc…
For actual documentation for how to do things/recommendation and troubleshoot, i use Jetbrains Space. Here my structure:

For backup, i add a log for each backup and post it on my chat channel which is also in the jetbrains space.
Multi-user documents edit is currently not yet available on jetbrains space but will be added soon :d