.drittel {
    width: 31%;
    display: inline-block;
    background-color: #c0c7e2;
    padding: 18px;
    border-radius: 24px;
    margin: 3px;
    text-align: left;
    vertical-align: top;

    @media (width <= 780px) {
        width: 99%;
    }
}