Thanks for the patch. To fix your problem with the german special characters, you need to change the font. Go to the Data folder and rename data.kfs to zip. Open the archive and put an other font in it (as example arial). Edit the fonts.cfg and change the font setting at the beginning to your new font. Save this settings and rename the zip-archive back to kfs. By this way you can also change the font size, if you need it for better reading.
I found this solution in the official forum:
http://forum.1cpublishing.eu/showthread.php?t=7870 There are btw many other mods for King's Bounty, just take a look into the forum.
Ah, another information about this language patch: The version of the game changed from 1.7 to 1.6.5. The game works fine, but I don't know what is different beside the language to the unpatched version.