Export as CSV format or is it the other one, I forget? One of them should work & you should be able to edit them in something like excel or the open office equivalent. The translations should be added into the same row.
As for the speech files... you will either have to manually link the relevant English speech file to each individual German text, or as a much faster & easier solution, you could just use Lua script to force the Speech Language to English.
game.SpeechLanguage = Languages["English"]
* edit #1: just checked the wiki. There's a page here
about exporting, importing & editing CSV text files.
* edit #2: you should also be able to manually update the paths in the csv files to add same speech file path to the german speech file paths - well if you don't mind the extra work & don't want to use the Lua method to force the engine to use x language for speech files.