I'm now working on kde 3.5.7. Now my questions to you guys: What translations are needed? Until now I've the german one and the default english?

Maybe these:

french
spanish
italian
turkish

kderepo you can find here:

http://paldo.org/~amnon/kderepo

Packages you can find in that repo:

• kdebase (3.5.7) - basic KDE desktop
  
• kdelibs (3.5.7) - the KDE libs
  
• arts (1.5.7) - the soundsystem of KDE
  
• kde-i18n-de - german translation of KDE
  
• kde-i18n-fr - french translation of KDE
  

use "upkg-build --verbose PACKAGENAME" for installing

other packages will follow also a KDE-livecd.