#berlin {
    background-image: url("https://i.pinimg.com/236x/67/df/87/67df872b61fc1bebe1c1b9ecf8f39893.jpg");
}

.gallery {
    width: min(100%, 800px);
    display: flex;
    flex-wrap: wrap;
    gap: 25px;
}

.gallery img {
    height: 400px;
}

@media screen and (max-width: 768px) {
    .gallery img {width: 100%; height: auto;}
}