i 've added new user story and its task, but how to reset all of the numberings to number #1?
From what I’ve seen each task, each task, each subtask increments the same number. You can test that.
If that is correct you’d end up with duplicate numbers.
You could always reset the number by finding it in Django or the database or maybe the api.
I wouldn’t worry about it - it’s immaterial - or start a new project.
Cheers
Keith