.headline {
    display: none;
}

@media (min-width: 700px) {
    .t3 {
        column-width: 33vw;
        column-gap: 1em;
    }
    main {
        grid-template-areas:
            "header   header   "
            "bbb      nav      "
            "bbb      article  "
            "section3 article  "
            "section3 t1       "
            "t2       section1 "
            "t3       t3       "
            "footer   footer   "
            ;
    }
}

    @media (min-width: 900px) {
    main {
    grid-template-areas:
        "header   header   header   nav      "
        "article  article  article  bbb "
        "section1 section1 t3       t3      "
        "t1       section3 section3 section3 "
        "t2       section3 section3 section3 "
        "footer   footer   footer   footer  "
    ;
}
}