Looking for a navigation that displays child categories..

I’ve tried countless navigations and have looked up a lot of coding and I can’t find a simple navigation that displays the main categories then once you click those categories the child categories are displayed..

This script almost works:
https://www.catswhocode.com/blog/wordpress-magazine-style-horizontal-dropdown-menu#comment-71574

It has some IE problems though, And the child categories disappear when you view a single post. I found another code:
https://www.ads-software.com/support/topic/297615

I don’t know if it will do the job because I have no idea how to make the child categories hide or anything so every single child category is displayed at all times by the code’s default which doesn’t work for a horizontal navigation.

Any help would be awesome!