How to hide header and navigation on desktop view only

Hi I want to hide my header section + Nav on desktop view only,  can someone help me with the code. 

florislandi.com 
password - test 

Yes, here's what you need:

#collection-63cfea0f11567d2c95675c56 {
  #header {
    display:none;
  }
}

Use media screen min-width. Adjust min-width as you want. Here is example code. 

@media (min-width: 768px) { 
  .header {
     display: none;
  }
}