@Quack; Kodu alt kısıma ekliyorum..
CSS :
/**
* -------------------
* ## Mega Menu
* -------------------
*/

.eduvibe-header-area ul.eduvibe-navbar-nav li.mega-menu > ul {
    display: flex;
    flex-wrap: wrap;
    overflow: hidden; /* Prevent content overflow */
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.2); /* Sönük gölge */
    border-radius: 8px; /* Kenar yuvarlatma */
    padding: 10px; /* İç içe kutu boşluğu */
}


.eduvibe-header-area ul.eduvibe-navbar-nav li.mega-menu > ul.eduvibe-dropdown-menu > li {
    display: block;
    margin: 0;
    width: 25%;
    border: none;
    font-size: 12px;
    font-weight: bold;
    transition: background-color 0.3s ease;
    position: relative;
}


.eduvibe-header-area ul.eduvibe-navbar-nav li.mega-menu > ul.eduvibe-dropdown-menu > li:before {
    content: "";
    position: absolute;
    bottom: 0;
    left: 0;
    width: 100%;
    height: 3px;

}

.eduvibe-header-area ul.eduvibe-navbar-nav li.mega-menu > ul.eduvibe-dropdown-menu > li:hover {
    background-color: #c5c7ff;
        overflow: hidden;
}

.eduvibe-header-area ul.eduvibe-navbar-nav li.mega-menu > ul.eduvibe-dropdown-menu > li:hover:before {
    background-color: #ff6601;
}




.eduvibe-header-area ul.eduvibe-navbar-nav li.mega-menu>ul.eduvibe-dropdown-menu>li>a {
    border-bottom: 0.5px solid #ffffff;
    border-radius: 0;
    font-size: 14px;
    line-height: 2;
}

.eduvibe-header-area ul.eduvibe-navbar-nav li.mega-menu.hide-header>ul.eduvibe-dropdown-menu>li>a,
.eduvibe-header-area .eduvibe-mobile-menu-nav-wrapper li.mega-menu.hide-header>ul>li>a,
.eduvibe-header-area .eduvibe-mobile-menu-nav-wrapper .metismenu li.mega-menu.hide-header .sub-menu.mm-collapse {
    display: none;
}

.eduvibe-header-area .eduvibe-mobile-menu-nav-wrapper li.mega-menu.hide-header>ul {
    padding-left: 0;
}

.eduvibe-header-area .eduvibe-mobile-menu-nav-wrapper .metismenu li.mega-menu.hide-header.mm-active .sub-menu.mm-collapse,
.eduvibe-header-area .eduvibe-mobile-menu-nav-wrapper .metismenu li.mega-menu.hide-header.mm-active .sub-menu.mm-collapse:not(.mm-show) {
    display: block;
}

.eduvibe-header-area ul.eduvibe-navbar-nav li.mega-menu>ul.eduvibe-dropdown-menu>li>a:hover {
    color: #272727;
    background-color: inherit;
}

.eduvibe-header-area ul.eduvibe-navbar-nav li.mega-menu>ul.eduvibe-dropdown-menu>li ul {
    position: relative;
    width: 100%;
    left: inherit;
    -webkit-box-shadow: none;
    box-shadow: none;
    background: inherit;
    padding-top: 10px;
    padding-bottom: 10px;
}

.eduvibe-header-area ul.eduvibe-navbar-nav li.mega-menu>ul.eduvibe-dropdown-menu>li ul li {
    padding: 0;
}

.eduvibe-header-area ul.eduvibe-navbar-nav li.mega-menu:hover ul {
    opacity: 1;
    visibility: visible;
    -webkit-transform: scaleY(1);
    transform: scaleY(1);
}


/**
JS :
    let eduVibeMegaMenu = function() {
        if ( "rtl" == document.dir ) {
            $( '.main-navigation ul > li.mega-menu' ).each(function() {
                let items       = $(this).find( ' > ul.eduvibe-dropdown-menu > li' ).length,
                bodyWidth       = $( 'body' ).outerWidth(),
                parentLinkWidth = $(this).find( ' > a' ).outerWidth(),
                parentLinkpos   = $(this).find( ' > a' ).offset().left,
                width           = 1100,
                left            = width / 2 - 500 - parentLinkWidth / 2,
                linkleftWidth   = parentLinkpos + parentLinkWidth / 2,
                linkRightWidth  = bodyWidth - (parentLinkpos + parentLinkWidth);

                if (width / 2 > linkleftWidth) {
                    $(this).find( ' > ul.eduvibe-dropdown-menu' ).css( {
                        width: width + 'px',
                        right: 'inherit',
                        left: '-' + parentLinkpos + 'px'
                    } );
                } else if (width / 2 > linkRightWidth) {
                    $(this).find( ' > ul.eduvibe-dropdown-menu' ).css( {
                        width: width + 'px',
                        left: 'inherit',
                        right: '-' + linkRightWidth + 'px'
                    } );
                } else {
                    $(this).find( ' > ul.eduvibe-dropdown-menu' ).css( {
                        width: width + 'px',
                        right: '-' + left + 'px'
                    } );
                }
            } );
        } else {
            $( '.main-navigation ul > li.mega-menu' ).each(function() {
                let items       = $(this).find( ' > ul.eduvibe-dropdown-menu > li' ).length,
                bodyWidth       = $( 'body' ).outerWidth(),
                parentLinkWidth = $(this).find( ' > a' ).outerWidth(),
                parentLinkpos   = $(this).find( ' > a' ).offset().left,
                width           = 1100,
                left            = width / 2 - 100 - parentLinkWidth / 2,
                linkleftWidth   = parentLinkpos + parentLinkWidth / 2,
                linkRightWidth  = bodyWidth - (parentLinkpos + parentLinkWidth);

                if (width / 2 > linkleftWidth) {
                    $(this).find( ' > ul.eduvibe-dropdown-menu' ).css( {
                        width: width + 'px',
                        right: 'inherit',
                        left: '-' + parentLinkpos + 'px'
                    } );
                } else if (width / 2 > linkRightWidth) {
                    $(this).find( ' > ul.eduvibe-dropdown-menu' ).css( {
                        width: width + 'px',
                        left: 'inherit',
                        right: '-' + linkRightWidth + 'px'
                    } );
                } else {
                    $(this).find( ' > ul.eduvibe-dropdown-menu' ).css( {
                        width: width + 'px',
                        left: '-' + left + 'px'
                    } );
                }
            } );
        }
    }
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