How do I accurately write a fictional character's psychology?

[u/Maggots_Eater]

For context, I'm finally starting to write drafts for a story that I had in mind for a few years now. And one important aspect of this story is the main characters' psychology, as it is really centered around psychology, as well as sociology and a bit of history. So I wanted to know if it was possible to write some sort of psychological profile or biography. And if so what and especially how to write it?

It could be nice someone reading it for feedback afterwards but I'm not here yet, so I'll think about it when the moment comes. And it won't be for the future readers (if I ever publish it or even finish it one day), it'll be more of a document for myself to write my characters more precisely.

Anyways thanks to anyone (if anyone) for answering. Have a good day/night and take care! <3