I dug around a little bit, and it looks like the script and audio files for Breakout are not encrypted in any way, so it's possible to make the game use German voices and English text (or vice versa). What you need to do is open "<game directory>\data\speech_en.jar" and "<game directory>\data\speech_de.jar" with an archive program (I recommend
7-zip, but WinRAR or similar should also work) and copy all of the files inside the German one (speech_de.jar) into the English one (speech_en.jar). (Note! Make sure to backup the files before editing them!)
There are some extra/missing files, so there might be leftover English bits, and I didn't do much testing so there might be some crashes somewhere, but everything seemed to work fine, and if there are any crashes you should be able to swap back to the default files just for long enough to get past any problem areas.
Unfortunately the files from Harvey's New Eyes seem to be either compressed in a non-standard manner or encrypted, so I have no idea how to edit them.