@ Wolfgang
The issue you are experiencing can only be fixed by the theme dev. Unfortunately there is nothing I can do to fix it from my side. I’ll explain.
The update to WordPress 4.5 included an update to jQuery version 1.12. That jQuery update fixed a bug, the details of which you can read about in this post by the WordPress developers.
The theme in the themify.scoll-highlights.js file on line 64 and 189 has an error it its code which is the bug that jQuery 1.12 fixed which is now causing this fatal JavaScript error you’re seeing. This fatal JavaScript error is basically breaking Javascript throughout your site which means any plugin that needs it may not work.
I see your site is running version 1.6.7 of the theme and it seems the current version of that theme is 1.9.3 so they may have already have fixed the issue. So the solution is likely to update your theme. I recommend contacting the theme’s support.
I hope that helps! Let me know.