Dear Heike Cordes,
I am afraid the above will not be a structural solution and I suppose following the below will help us resolve the issue.
1. Re-Install Oracle as Enterprise Edition which enables partitioning. (or)
2. Follow sap note - 370819
PFB link for your reference.
https://community.oracle.com/thread/977087
Note 370819 - ORA-439: Feature not enabled: Partitioning - Sap NOTE Sap-ConsAlt.Ru
Please correct me if I am wrong.
Regards
Baranedharan S.