header{
    background-image: url(../img/francfort.jpg);
    background-position-y: 0px;
}

span.header_cover{
    display: block;
    position: absolute;
    opacity: 0.2;
    width: 100%;
    height: 100vh;
    background-color: black;
}

header h2{
    color: #fff;
    text-shadow: 0 0 25px rgba(0,0,0,1);
}