drupal-reha/web/themes/custom/reha/scss/partials/_header.scss

    header{                       
        display: block;
        width: 100%;
        background-color: white;
        position: fixed;
        z-index: 99;
        width: 100vw;

        position: -webkit-sticky;
        position: sticky;
        top: 0;
        .sticky{
                position: fixed;
        }
        div{
            display:flex;
            flex-direction: row;
        }
    }