.banner-about {
    display: flex;
}

.banner-about__item {
    flex-grow: 0;
    flex-shrink: 0;
    flex-basis: 50%;
    width: 50%;
}

.banner-about__item img{
    width: 100%;
    height: 100%;
    object-fit: cover;
    max-width: 960px;
}
@media screen and (max-width: 767px) {
    .banner-about{
        flex-wrap: wrap;
    }
    .banner-about__item{
        display: none;
        flex-basis: 100%;
    }
    .banner-about__item:nth-child(1){
        display: block;
    }
}