I don’t really plan my stories! I have a “global” idea of what my story will be about and how I will bring it to the readers.
By writing, ideas come in my head, and sometimes, ideas come in my head but not at the right time. For example, I can have an idea at 3 am and write it in my notes right away to not forget it.
But to remember the personalities of my characters to know how they will behave, I create a table on Google Docs for them (age, relationships, etc…)
Sometimes, I write the dialogue in advance when I know what I want to happen next.
Idk if this is going to help but, this is how I do!