How to work with z-index?

Question

css

On the site, the photo is enlarged in the modal window, how to make the fixed navbar go under it, and not burn and function from above

Answer 1

Imagine any element with position:absolute; like a book, and now put all such books in a pile. Whichever element has the highest z-index will be the highest.

Answer 2

htmlbook.ru/css/z-index
https://htmlacademy.ru/courses/45/run/19
Well, give them a z-index...