.hej::before {
    content: '';
    position: fixed;
    z-index: -1;
    display: block;
    top: 0px;
    left: 0px;
    bottom: 0px;
    right: 0px;
    background-image: url('assets/bgbiggo.webp');
    background-size: cover;
    background-repeat: no-repeat;
    background-position: center center;
}

@media (max-width:767px) {
    .hej::before {
        background-image: url('assets/bgbiggomobo.webp ')!important;
    }
}