.maincontent{
max-width: 80%;
}

@media screen and (max-width: 1200px) {
    .gallery-item {
        flex: 25%;
        max-width: 24.5%;
    }
}
@media screen and (max-width: 800px) {
    .gallery-item {
        flex: 50%;
        max-width: 49.5%;
    }
}
@media screen and (max-width: 500px) {
    .gallery-item {
        flex: 100%;
        max-width: 100%;
    }
    .gallery-item {
        height: auto;
        display: block;
    }
    .gallery-item img {
        width: 100%;
        height: auto;
    }
}