Hello Ozgur
Please make sure you are using the correct format for the POST URL:
/content/site/<site name>/<culture>/document/<alias path>
the alias path is the full path of the first document you created, so if you are creating a new French culture version of the News page on CorporateSite it would be this:
~/rest/content/site/CorporateSite/fr-fr/document/News
then in the data you need to specify NodeID, however you should not explicitly set the DocumentID as this should automatically generate when adding the new culture version.