header #et-top-navigation ul#mobile_menu { background-color: #808080 !important; opacity: 1 !important; z-index: 9999 !important; }
.et_pb_column.et_pb_column_4_4 {

z-index: 1;

}

Add !important to it

.et_pb_column.et_pb_column_4_4 {

z-index: 1 !important;

}