Fixed Header ps 1.6

[frankmujik]

Hi, I was wondering if is it possible to have a Fixed Header but  when scrolling down the Nav Bar stay up or hide.. (see img)

 

I´ve tried editing some lines but I can´t figure it out

 

it is my header

 

header {
  z-index: 1;
  position: fixed;
  background: #d21834;
  width:100%  }