.wp-block-post-template.is-style-three-two-one {
    grid-template-columns: repeat(3, minmax(0, 1fr)) !important;
}

@media (min-width: 600px) and (max-width: 782px) {
    .wp-block-post-template.is-style-three-two-one {
        grid-template-columns: repeat(2, minmax(0, 1fr)) !important;
    }
}

@media (max-width: 600px) {
    .wp-block-post-template.is-style-three-two-one {
        grid-template-columns: 1fr !important;
    }
}