Add full width header

Hello!

I changed the theme of my website yesterday (Rush theme) but did not see that it wasn’t supporting headers…

I am now trying to create the get header image function manually, I managed to do someting in the functions.php section but I do not really know what I should do in the header.php section.

When I try to put some code in the header.php my header appears on the top of the website container, above the logo.

What I would like is having a full width header that replaces all the white background above the menu, and with the logo and the news ticker visible on it.

Could anyone help me? the website is http://www.thescanpost.lu/

Thank you in advance 🙂