Fixar menu em site Wordpress

Fixar menu em site Wordpress.css

#site-header.navbar-fixed-top{
	display: block;
}

.navbar-fixed-top{
	position: fixed!important;
	z-index: 998;
	background: #FFF;
	top: 0;
	left: 0;
	width: 100%;
	animation-name: fadeInOpacity;
	animation-iteration-count: 1;
	animation-timing-function: ease-in;
	animation-duration: 0.5s;
}

.navbar-fixed-top #site-logo-inner a img{
	height: 100px
}

.margin-main-fixed{
  margin-top: 255px;
}

Fixar menu em site Wordpress.js

const menu = document.getElementById("site-header");
		const mainContent = document.getElementById("main");
		document.addEventListener("scroll", function(event) {
			var scroll = window.scrollY
			if (scroll > 300) {
				menu.classList.add("navbar-fixed-top");
				mainContent.classList.add("margin-main-fixed");
			} else {
				menu.classList.remove("navbar-fixed-top");
				mainContent.classList.remove("margin-main-fixed");
			}
		});