I downloaded the german version of the game here, but the only manual I got is the english one. Where can I get the german one?

You can't, if it isn't among the extras then they don't have it here. However, the manual is pretty useless anyway, it's huge but does a poor job at explaining the basics. The most useful part are the tables in the appendix and for anything else I recommend the Wiki:
http://masterofmagic.wikia.com/wiki/Master_of_Magic_Wiki
The Klackon race has been translated as "horned ones" in case you were wondering. Klackons are an alien race from Master of Orion, but I guess the person writing the translation didn't know that and just looked at the sprites and said "whatever, they got horns, so they are the Horned Ones". (and yes, I know this is an old thread, but it didn't have an answer)

Thanks for the answer! I didn`t believe to get an answer after this long time, so you are very welcome!!!

You can find the game on Ebay occasionally. Right now the German version is sold in its original wrapping for 60€.

60€? Do they believe that I have a "Geldscheisser"? But thanks for the info!