DB owes you only 25% of the ticket price for your train fare. As far as I know, there is only one exeption, if you bought a "rail and fly ticket". A few month ago there was a court decision, that than this ticket is part of your overall journey. If you have such a ticket, I can take a look and a reference. However if you just bought a single ticket Berlin-SXF, you don't get much more than 25% of your ticket.
757DUD

As a side note, if DB sells you a ticket in one envelope, it is one contract, regardless how many different tickets are in this envelope. At least according to their own terms(p. 4, 2.4.2).