I lived in Germany for 11 years (2000-11) and worked the last 4 of those at a design/build firm that has built several of these pools: http://www.grothe-neue-gaerten.de. I also freelanced for a similar company that builds several each year: http://www.gaerten-von-gaertner.de.
It is really not that difficult, and the possibilities for design are endless. You can see a variety of styles by checking out these company websites. For starting out, it might be easiest to combine a preform pool with a biofilter system and plant filter zone rather than dealing with either concrete pools or pool liners for the swim zone.
If you need any help with German translations, feel free to pm me.