If you want to start translating, you should start with a
menu-messages.po[t] file. Really, we should distribute that
file somewhere on www.debian.org, but that hasn't been done yet.
To generate it temporarily from the menu entry files installed
on your system, type

  make menu-messages.pot

Then you simply type
  mv menu-messages.pot de.po
if you want to start making the german translations.

The Makefile in this dir really needs fixing up, but I'll do
that soon anyway. Probably before you manage to send in your
??.po file.

Thanks,
joost    <joostje@debian.org>