Giulio Daprela

Yes, just how I imagined, the CSS file doesn’t give any height and width for the header because they are already given in the html. If the custom.css doesn’t work the file you must modify is definitely header.php. Have you created a child theme? This is necessary, or any modification made will be deleted at the next theme update.
If you don’t know how to do it create an admin user and send me the credentials. I’ll do it for free of course. My address is [email redacted]

I don’t see any white background on that menu, I see instead a gradient from dark red to a slightly lighter red.
In any case, if you want to change that color you must first create a child theme, and then go to edit css and add the following instruction. The meaning should be clear even if you don’t know CSS. Background is the directive that changes the background. However, there are three different instructions, one for the Chrome browser (webkit), one for Firefox (moz) and one for IE. They all create the gradient that I see. You must change the colors of the gradient, if you use Firebug on Firefox or the developer tools on Chrome you should be able to test it.

#navmargins {
background: #340b0a;
background: -webkit-gradient(linear,left top,left bottom,from(#0f0201),to(#340b0a));
background: -moz-linear-gradient(top,#0f0201,#340b0a);
background: transparent\9;
filter: progid:DXImageTransform.Microsoft.gradient(startColorstr=’#0f0201′,endColorstr=’#340b0a’);
box-shadow: 0 1px 2px #000;
-moz-box-shadow: 0 1px 2px #000;
-webkit-box-shadow: 0 1px 2px #000;
}

You should give more information, or no one will be able to help you. Which themes were you trying to use? Have you already installed some plugins? Sometimes there are compatibility problems between plugins and themes. You should try to disable all your plugins and then install the theme to see if the problem comes from some plugin.

Sorry, also the theme name is mandatory, but here you can write whatever you want

A child theme inherit all of the files and configurations of the parent theme but you usually can override any of the parent theme configurations at your will provided you know what to touch.
With the child theme, you won’t lose any of your customization when the parent theme is updated.

If you uploaded your images through the media library they won’t be canceled or overwritten. You “lose” them only when you activate che child theme if they’ve been uploaded via ftp in the directory “images” in your parent theme’s directory. In that case you should move them in your child’s theme directory or upload them via the media library

Have you tried looking for a theme with similar layout but that is still supported? I think this would be the best soultion