Multi-language menu's / menu-items setup
At the moment it is not possible to translate the menu items in the node form:


  Unfortunately the node form's menu widget was not made ready for menu
  item translations (yet), so if you provide the French menu item title
  there, it will be updated in the original item and not going to create
  a translation. Until that is fixed, use the menu item translation
  process as with the contact menu item.


Drupal 8 multilingual tidbits 20: combination use cases with content and menus

The solution presented by Gábor Hojtsy in the link is to translate the menu in the menu management or use different menus for every language.