#scherenteile {
    max-width: 700px;
    margin: 3rem auto 0;
}
#hintergrund {
    position: fixed;
    top: 0;
    height: 100vh;
    width: 100%;
    background-image: url('../bilder/groessenangaben.jpg');
    background-size: cover;
    background-position: 50% 50%;

        }