How to make a separate second level menu in WordPress?

Question

WordPress

How to make a separate second level menu in WordPress?
That is, you go to the page of the section and the menu of this particular section appears there,
as here

https://www.gazprom.ru/investors/

Answer 1

In register_nav_menus you register the menu for each section. And in each section display the corresponding menu.

Answer 2

__DIR__ and $_SERVER['DOCUMENT_ROOT'] return the full path for the server's filesystem, i.e. along with /var/www/
... the user uploads the image through the browser.

Answer 3

In any unclear situation, do var_dump(); :)=)

Answer 4

$images = $_SERVER['DOCUMENT_ROOT'] . '/images/cat.jpg';
oh yes, and isn't it easier to output without variables through just html?