.watermark {
    position: fixed;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 100%;
    height: 100%;
    background-image: url('https://pelika-lab.de/welcome/assets/images/Pelika.png');
    background-repeat: no-repeat;
    background-position: center;
    background-size: contain;
    opacity: 0.2;
    z-index: -1;
}