Uncaught ReferenceError

Hello,

hopefully I am in the right section.
I am in the finishing process of a friends webshop. Currently I was working on page optimization and tried W3 Total Cache in combination with several online site checks to get an idea of what w3tc can do for me.
Lots of my goals were achieved with short code snippets, therefore I decided to uninstall W3TC.
Later I realized I have an error in console:
Uncaught ReferenceError: r is not defined
at (index):801
According to the fact I am a coding beginner, I had my difficulties to dig into this, but now I think I have an idea.
To allows the r character to be defined as the jQuery object, I need to add
(function($) {
to the top of code and
})(jQuery);
at the end of it.
(Source: https://www.thecreativedev.com/solutionuncaught-referenceerror-is-not-defined-in-wordpress/)
But to which script do I add this?
The site I am reffering to:

Any help is appreciated! Thanks a lot!

-Bj?rn

• This topic was modified 7 years ago by Jan Dembowski.
• This topic was modified 7 years ago by Jan Dembowski. Reason: Removed redundant link

The page I need help with: [log in to see the link]