Hi,
Please understand that this is a theme modification and I do not provide support for those (please read https://support.webmandesign.eu/support-policy-and-terms-of-service/).
I suggest you use a code inspector in your browser to determine the styles you need to override with your custom CSS. Also, I suggest you test your new layout thoroughly than as the theme wasn’t designed that way.
You can start with this CSS:
.is-singular:not(.home) .site-inner {
width: calc(100% - 5rem);
}
.is-singular .entry-media {
position: relative;
width: 100%;
background: none;
}
.is-singular .entry-media img {
visibility: visible;
}
But where do you put the header than?
Regards,
Oliver