It seems you've installed a new plugin or updated some plugin which generates JS error on front-end. Please deactivate all recent added/updated plugins, delete all caches and check it.

JS error comes from this code:

Try to use jQuery instead of $

If you want to use $ instead of jQuery all the time you can run your code in a separate, private scope that holds the definition of $ by using a self-invoking function.

(function($){
 // your code with $ goes here
})(jQuery);

In any case if you can't fix this JS error, please remove it.

Thank you very much for the help but I do not know how to fix the error. I'm working on it and nothing works for me. 🙁

Have you tried to remove this JS code?