Without you being more specific, I can't be entirely sure what you are after, but Sebastian Conrad's German Colonialism: A Short History (which does exist in English) is a good introduction to the topic, and the selected readings towards the end provides a good bibliography for a variety of topics he touches upon - it has been on our undergraduate reading list for European colonialism for a year or two now.

However, if you want something more focused, just ask away and I will try to help