Problem is solved! I took a look at the core-files (content-portfolio-single.php) and found the solution. I put this php-snippet in the content-page.php:
<?php// Access global variable directly to adjust the content width for single page
if ( isset( $GLOBALS['content_width'] ) ) {
$GLOBALS['content_width'] = 1100;
}
?>
Then I changed in the custom-css the class “entry-content” from 840px to 1100px. Great on a large screen but bad for the smartphone-view. That’s why I modified the css, that it effects only large screens:
@media screen and (min-width: 1220px) {
.entry-content {
width: 1100px;
}
}
It works nice and my problem is solved.
Regards, Andreas