You must have valid health insurance, to enroll at a German university!
Applicants from within the European Union:
You do not need a German health insurance policy. Your European Health Insurance Card (EHIC) is valid and sufficient. You have to order the European Health Insurance Card (EHIC) from your insurance company in your home country well in advance.
Applicants form beyond the European Union:
For you a German health insurance policy is obligatory. After you arrival in Frankfurt (Oder) you have to conclude such a policy with a German health insurance company.