#sept1 {

    height: 500px;
    background-image: url(https://images.biggeek.ru/images/1sept_2025_bts_mob.jpg);
    background-size: 800px 500px;
    background-repeat:no-repeat;
    background-position: center center;

    @media (min-width: 800px) {
        height: 500px;
        background-image: url(https://images.biggeek.ru/images/1sept_2025_bts_tab.jpg);
        background-size: 1200px 500px;
    }

    @media (min-width: 1200px) {
        height: 500px;
        margin-bottom: 10px;
        background-image: url(https://images.biggeek.ru/images/1sept_2025_bts_desk.jpg);
        background-size: 1420px 500px;
    }

}