@media only screen and (max-width: 992px) {
    .slider{
        background-image: url('../images/992-01.png');
    }
}
@media only screen and (max-width: 768px) {
    .slider{
        background-image: url('../images/768-01.png');
    }
}
@media only screen and (max-width: 576px) {
    .slider{
        background-image: url('../images/576-01.png');
    }
}
@media only screen and (max-width: 414px) {
    .slider{
        background-image: url('../images/414-01.png');
    }
}