after doing german language patches for the other settler installments i thought i might do one for this game as well:

http://www.gog.com/forum/the_settlers_series/german_language_patches_for_all_settlers_games

before using it you should make a backup of your /base/lang.bba file, because like my other patches i dont have the time to test everything. as always, point the installer to your Settlers 5 directory.