body {
    background-image: url('foto/cloud.jpg');
    background-size: cover;
    background-position: center;
    background-attachment: fixed;
    background-repeat: no-repeat;
}
.gallery {
    display: flex;
    flex-wrap: wrap;
    justify-content: space-between;
    margin: 20px 0;
}

.gallery img {
    width: 20%;
    margin-bottom: 20px;
}