Once again, Allana may not be interested in this anymore after eight years, but anyway...
I remember that the first entries in the journal are made by a script. Thus, the german texts for these entries are in that script, not in the journal area accessible with the TES III Construction Set. I once tried to change that, but failed. Somehow, I am unable to get changed scripts to work with "Myar Aranath".
Another place where a script may still use text in German is in the Tersulen forest. A certain action there might trigger an on-screen message like "Tretet ein, Volstrecker!" ("Come in, executor!"). However, the quest connected to this message is unfinished anyway, so... -shrug-