Chrystl on "Polylang. Traslated menu is not working"

Not sure but maybe an issue with ajax. Themes with ajax don't work with multilinguale sites.
But you can test :
=> with a default WP theme like Twenty twelve + only Polylang and other plugins deactivated. If it works:
=> activate your plugins other plugins one by one.
If it works it's certainly a conflict with your theme.
Could ask to your theme author to disable the ajax. Some themes have this setting.