#box_7{
display:none;
}
@media(max-width:999px){
  #box_7{
  display:block;
  background-image:url("https://turniejowo.pl/rezerwacje/slider/slide-2.jpg");
    background-size:cover;
    background-position:center;
  width:100%;
    height:600px;
    position:relative;
  }
  #box_7::after{
  content:'';
  position:absolute;
  top:0;
  left:0;
  width:100%;
  height:33%;
  background:linear-gradient(0deg, rgba(0,0,0,0) 0%, rgba(0,0,0,.5) 24%, rgba(0,0,0,1) 80%)
  }
#box_7 > div > img{
  width: 92%;
    position: absolute;
    bottom: auto;
    left: 50%;
    transform: translateX(-50%);
    top: 145px;
  z-index:999;
  }
}