Hello again,
when I choose a PRO Header and/or a PRO Footer - there is the error message.
When I choose the normal X Theme Top Bar with menu or the normal X Theme Footer with menu, I get the error message - for example:
`
Fatal error: Uncaught InvalidArgumentException: Argument ID must be numeric and greater than 0. in /www/htdocs/w00e1ede/hp_2017/wp-content/plugins/sitepress-multilingual-cms/classes/translations/class-wpml-translation-element.php:28 Stack trace: #0 /www/htdocs/w00e1ede/hp_2017/wp-content/plugins/sitepress-multilingual-cms/classes/translations/class-wpml-term-element.php(19): WPML_Translation_Element->__construct(NULL, Object(SitePress), Object(WPML_WP_Cache)) #1 /www/htdocs/w00e1ede/hp_2017/wp-content/plugins/sitepress-multilingual-cms/classes/translations/class-wpml-menu-element.php(17): WPML_Term_Element->__construct(NULL, Object(SitePress), ‘nav_menu’, Object(WPML_WP_Cache)) #2 /www/htdocs/w00e1ede/hp_2017/wp-content/plugins/sitepress-multilingual-cms/classes/translations/class-wpml-menu-element.php(27): WPML_Menu_Element->__construct(NULL, Object(SitePress), Object(WPML_WP_Cache)) #3 /www/htdocs/w00e1ede/hp_2017/wp-content/plugins/sitepress-multilingual-cms/classes/translations/class-wpml-translation-element.php(108): in /www/htdocs/w00e1ede/hp_2017/wp-content/plugins/sitepress-multilingual-cms/classes/translations/class-wpml-translation-element.php on line 28
`
For now, I can work with no topbar and no footer menu and translate the page. I will look for the error when the translation is done.