How to make a shadow at the bottom of the menu stick?

Question

css

There is a site that is being done on wp, I want to make the sticky menu cast a shadow only at the bottom.
When the page is not scrolled and the meta grabs the header and fits completely into its area, then the shadow does not drop. Like this: My real menu on which I want to make a shadow (the shadow disappears when everything is fine):
When you scroll the header will go into the sunset and only the menu sticks at the top remain, then a shadow should appear at the bottom of the menu. Example :
As an example, a real site. I want to do something similar. Preferably without js if possible since I work on Wordpress (scroll): https://zdravcity.ru

Answer 1

It's simple:
use CSS box-shadow
And here's a generator so you don't have to write it yourself - https://www.cssmatic.com/box-shadow
Here's an instruction on how to create a fixed header - https://www.w3schools.com/ howto/howto_js_sticky_he...