.content-bg {
    background-image: url("../lib/img/bg/impressum-1080.jpg");
    opacity: 0.25;
}
@media all and (min-height: 1440px) { .content-bg { background-image: url("../lib/img/bg/impressum-1440.jpg"); } }
@media all and (min-height: 2160px) { .content-bg { background-image: url("../lib/img/bg/impressum-2160.jpg"); } }