When u say the German version, then you definatley mean you got the german-dubbed language. Wing III and Wing IV were ported to as many different languages in Europe and it is stilled within the game so unfortunatley i dont think there is a way to configure the language at all in normal settings or in any other diverse way.
Exploring the files located in the WC folder mite give you clues but i dont no. Ages ago i acquired the bloody french version for Wing IV and i would like to know if there is/was any way to sort that out. (probably grabbing an English Language TRE.file) im talking nonsense here but ur really out of luck friend.
What you can do, is grab the Win95 patch (english), specifically built for Wing IV, install the game using the patch and check the option for subtitles. Start the game by clicking on the patch and it WILL come up with ENGLISH subtitles - albiet in a German-dubbed voiceover -
Or you can jus go on Ebay.co.uk and buy a Wing IV games under the proper version. I dont know anything about Prophecy though. hope this helps.