Contact form7 Datepicker doesn′t work in firefox, safari

Hi, i think many people have the problem with the Datepicker in Contact form 7 wich is not working in firefox, safari and so on! Only Chrome shows!

Of course before i created this topic i was searching for answers for this problem. I have found this -> wpcf7_support_html5_fallback’, ‘__return_true -> adding in the funktions PHP -> but it doesn′t work. I have also found answers that i should change the theme -> that can′t be the solution for that!

Maybe somebody can help me ??
here is the link where the Form is: https://www.creative.js-creative-services.com/octopusrestaurant/wordpress/reservierung/

Thanks in advance