When I click on a portfolio item, the language parameter in the url (lang=xy) is reseted.
Where can I modify this behavior?
WPML will save the current language in a cookie and you don’t need the &lang parameter. In addition Kriesi added some permalink rewrite rules to wp-contentthemesenfoldconfig-wpmlconfig.php (which replace the default &lang parameter) if you want to use pretty permalinks with WPML. Other translation plugins (like qtranslate) are currently not supported by Enfold and may not work as expected.