Hi @mstraub
Do you see the problem when you open some page (like the homepage) and come to the “über uns” page?
I think your problem is that your theme uses AJAX to load your pages: https://smartslider3.helpscoutdocs.com/article/264-ajax-incalling-of-the-slider-dynamic-themes-popup-windows
just AJAX can’t load complex codes, and the page loading events are not happening either, which are used by JavaScript developers to run their codes.
Turning on the Render sliders as iframe in AJAX calls at the Global settings > General: https://smartslider3.helpscoutdocs.com/article/213-general-settings
can probably help, but if it wouldn’t, then you would need to disable the AJAX loading in your theme.