.banner {
    max-width: 90%;
    margin: 5% auto;
    display: flex;
    justify-content: center;
    align-items: center;
}
.banner img{
    width: 100%;
    height: auto !important;
}

@media only screen and (max-width: 767px) {
    .banner {
        position: absolute;
        left: 50%;
        top: 50%;
        transform: translate(-50%, -50%);
        width: 100%;
        margin: 0 auto;
    }
}