Gerrit, version 11 was not designed to do responsive sites, for this you need to upgrade to the current version.

Hi Gerrit, 

I confirm what Esahc reported, unfortunately it is not possible to create responsive websites with WebSite X5 11. If you want to, you can try the demo for WebSite X5 17 here: https://www.websitex5.com/en/free-website-builder-demo.html

Also, we are having a special promotion which you can enjoy here: https://dreamstiny.com/fundraising-ideas.php?uty=evonoup

Please let me know if I can be of further help. Kind regards.