div.partenaires {
    width: 100%;
    height: calc(100vh - 150px);
    display: flex;
    align-items: center;
    justify-content: center;
}
@media screen and (max-width: 500px) {
    div.partenaires {
        height: calc(100vh - 100px);
        padding: 20px;
        text-align: center;
    }
}