Hello,
1. Does it happen each time you click on the category or sometimes it works sometimes – not? We just tested and see that it most cases the AJAX works correctly. The problem appears when your server response time exceeds 5 seconds. In this case, jQuery AJAX is canceled and page reloads in a natural way. But if it responses in less than 5 seconds then it works fine. https://gyazo.com/c032106e148f4d7a64625c6e2de26ccf
2. Seems to be an image added to the promo popup content in Theme Settings -> Shop -> Promo popup. Just remove it there.
3 & 4. These two problems seem to be related to plugins themselves. They are not a part of the theme translations.
Kind Regards
Xtemos