body {
    background-image: linear-gradient(rgba(0, 0, 0, 0.3), rgba(0, 0, 0, 0.3)), url(assets/image1.jpg);

    background-size: cover;
    background-repeat: no-repeat;
    background-position: center;
    width: 100%;
    height: 100vh;
    position: relative;
}

header {
    width: 100%;
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
}