That is the Site of your title. http://prntscr.com/mx72tc you can also change that in the Appearance > Customize > Header > Logo > Text Logo. http://prntscr.com/mx7305

Kind Regards

Hey Javier,

You can add it with Custom CSS. http://prntscr.com/nfbvq4

As a property to the logo.

.a-logo.a-logo--image a:after {
  content: 'Logo';
  position: absolute;
  top: 40px;
  color: #fff;
}

Feel free to ask for anything you need.

Kind Regards

I am sorry but making that fullscreen is not available on Centaurus, it will require a lot of extra work.

You can change the background color.

.l-primary-header.l-primary-header--responsive .l-primary-header--responsive__nav nav ul.menu {
    background-color: your_color !important;
}

To change the color

.l-primary-header.l-primary-header--responsive .l-primary-header--responsive__nav nav ul.menu li.menu-item a {
    color: your_color !important;
}

This is the main selector, to change the height.

.l-primary-header--responsive .l-primary-header--responsive__nav

Feel free to ask for anything you need.

Kind Regards