<a class="hum" href="#">
.hum {
background: url(icons/humburger.svg);
background-size: 100%;
}
<a class="hum hum2" href="#">
.hum2 {
background: url(icons/close.svg);
background-size: 100%;
}
.hum2 {
background: url(icons/close.svg)!important;
background-size: 100%;
}