Header Image not responsive

Hello,

After 3 days of researching the problem, I still can’t fix it.
Could someone please help me how to fix the Image header from disappearing when I make the screen smaller? I don’t mind to make the menu (navbar) location also responsive, in way that it will go up or down. I understand the image size is not standard, but I try to work with it.

Many thanks
Mike

http://www.silatehilim.com