body {
    width: 100vw;
    height: 100vh;
    margin: 0;
    background: url(../img/bg.jpg) no-repeat center center / cover;
    display: flex;
    align-items: center;
    justify-content: center;
}
body:before {
    content: "";
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    z-index: 0;
    background-color: rgb(49 61 71 / .7);
}
.site {
    position: relative;
    z-index: 1;
    margin: 0 auto;
}