Also, I’ve got some strange problem with the language switcher – it’s got a square as an icon, while it should be an arrow. That is valid for the “To the top” button.
your main menu is built in Elementor, and the Arrow icon is expecting a FontAwesome icon – but the site is not loading FontAwesome and its HTML is broken. Does the Switcher work correctly if you disable the Elementor Navigation and display the Themes navigation?