Reduce width of header dropdown, centre dropdown items, and change dropdown background on scroll

Hi, 

I am trying to customise my sites header. At the moment I have a dynamic heading on my pages, and I have used some custom code to get the transparent to change to black on scroll. I would like the header dropdown to do the same thing.

I also want to centre the dropdown items in line with the navigation links. I have used some custom code to centre the dropdown but they aren't in line with the nav links.  And I would like to reduce the width of the dropdown. At the moment the clickable padding on the nav links seems too big as the dropdown doesn't change immediately when I move between links (moving from 'products' to 'about' and back to 'products' is glitchy.

Site url: https://tortoise-saffron-fc2h.squarespace.com/about

Password: Turtle2000!

@tuanphan perhaps you might be able to help?

Turtle2000!

password is incorrect

Hi Tuan, sorry I have only just seen this response! The password is Turtle200!

You can add this to Website > Website Tools (under Not Linked) > Custom CSS

header#header.shrink div.header-nav-folder-content {
    background-color: black !important;
}