Thank you for your reply. The version I installed was a mod by Thomas Thane. latest version osticket_1.7.2-stable_ml_V10. (http://forum.osticket.com/d/discussion//mod-multilanguage-support/p1)
This version works fine but ends now, since the regular osticket version will contain language support. I'm not sure the tables are the same. I will try to upgrade (after backup) on a test version. I'll hope that the data after the upgrade will be retained. I've spent a lot of time in creating departments, groups etc