Morgend Joepioooo;
You have the same error without Autoptimize; cfr. this validation report.
The problem is with the value of the media-attribute on this line;
<link rel='stylesheet' id='retina-css' href='https://www.host-reviews.nl/wp-content/themes/inovado/framework/css/retina.css' type='text/css' media='only screen and (-webkit-min-device-pixel-ratio: 2)' />
The validator does not expect media-queries with vendor prefixes there (the dash in "-webkit").
Hope this helps,
frank