.bg-img1{
    background-color: black;
    background-image: url('../images/backgrounds/main-slider-1-1.webp') !important;
}

@media only screen and (max-width: 500px) 
{
    .bg-img1{
    
        background-image: url('../images/backgrounds/main-slider-1-1m.webp') !important;
    }
}