Changing the standard tutor theme

I recently installed Open edX from tutor. I want to change the standard theme. I managed to change such pages as index.html, footer.html . Next, I want to change the menu that I see when I enter the course.
For example, somewhere here https://apps.mydomen/learning/course/courseid/home
I think I should change this file here
edx-platform/course_navigation.html at master · openedx/edx-platform · GitHub

I have created the necessary folders and file in my theme, but I still see the old theme.
Which file should I change correctly?

And I have a question on header.html . Why is it different in different places? Which files should I edit?