I’m getting “INTERNAL SERVER ERROR” from your server when I click on your link.
Please get in touch with your hosting provider to have this resolved, so I can check the site and give you the CSS code.

If you have wanted to add an overlay for the homepage header, you can use the following CSS. Adding an overlay will help making the site’s logo and menu items easier to read.
.home header:before {
position: absolute;
content:"";
inset:0;
background: #000;
opacity: 0.4;
z-index: -1;
}
and add the following CSS if you wanted just a box shadow.
.home header {
box-shadow: -2px 0px 17px 7px #000000a6;
}
Hope this helps you.