/* 1. The Hover State (Your working code) */
.wp-block-navigation .wp-block-navigation-item a:hover,
.wp-block-navigation-item__content:hover {
    text-decoration: none !important;
    border-bottom: 4px solid #faa700 !important;
    padding-bottom: 2px !important;
}

/* 2. The Active/Current Page State */
/* This targets the specific page you are on AND the parent categories */
.wp-block-navigation .current-menu-item > a, 
.wp-block-navigation .current-menu-ancestor > a,
.wp-block-navigation .current_page_item > a,
.wp-block-navigation .current_page_ancestor > a,
.wp-block-navigation .current-menu-item > .wp-block-navigation-item__content,
.wp-block-navigation .current-menu-ancestor > .wp-block-navigation-item__content {
    text-decoration: none !important;
    border-bottom: 4px solid #faa700 !important;
    padding-bottom: 2px !important;
}