Actually, you can also claim for the loan itself, but only for the part of the loan that was for the tuition fee. You cannot claim for the part that was for your daily living expenses during the MBA.
But it is an uphill struggle, since uni is free in Germany, you first have to convince the people at the Finanzamt that there is something like a uni degree that costs 30,000€ and that there are people willing to pay that much!
Bring documentation on the tuition fee, all the invoices, uni transcripts, loan document, and so on.
But be prepared to be met with disbelief.