Go the the web interface http://<ip dreambox> and log in. Then go to Config, Settings. In there add the audio priority as follows: English#Englisch#Dutch#Deutsch#German

This line means if multiple audio streams are available it will use the English one first, if that is not available it will use the Dutch one and if that one is not available it will use the German audio stream.

Tip: Use the audio button to copy the exact audio names used by channels. Some channels have incorrectly spelled audio streams.