Remove header ad and expand custom header graphic

I just put up a new site and I’m new to WP.
Americaisconservative.org

I have the Max Magazine theme. There is an add banner in the top right, how do I get rid of it?

I have a custom picture for my header, how do I extend it to go across the whole top?

I was reading that to update the code I have to create a child template, so I’ve done that, just don’t know where to go from here.

Thanks.