Hello Metalab,

my father just posted the following on Facebook:

This is a question. The code was invented by me and
        a friend back in the 80s:

aCBLFDZHDFLMIY/PKJJTIFBPCZASGNYIGIWWTNJKXZAOKMTTUGQSGXENU

If someone should be able to read this, send me the
        correct answer. I can't imagine this code is breakable...

The
      result should be a German text, although he said he doesn't think
      this information would be helpful.

Who wants to try and break it?

      Have fun!

      Ben