Sorry to hear about the problems you've encountered. I'll try to offer some suggestions to help and point you in the right direction to resolve your other issues.
First, I believe the German version of MA was localized by a German firm that also sells and supports it. If you know that company and how to contact it, you can speak to them about their plans for MA 2 and their upgrade policies. If not, contact Prolific (go to
www.serenescreen.com and select the Technical Support page) to obtain directions to the German firm that sells/supports your version.
Second, when you say that you had problems with the Monitor preferences when using the screen saver, could you be more specific about your settings and what you're seeing? In the settings for the MA screen saver (or the app), do you have "Full screen resolution" set to anything other than "Desktop resolution" (or the German equivalents of these English phrases)? You may need to delete your preferences file (look in "~/Library/Preferences/By Host" and delete any file starting with "com.prolific.ScreenSaver.Aquarium"). If this doesn't solve the problem, please let us know.