Language change in Ubuntu - files not transfered to new paths
Solution 1:
The behavior you describe is intentional. Empty standard folders are simply renamed, while non-empty are not. The reason is to not break the old file paths automatically. New files saved to ~/Desktop will end up in the new folder.
You can easily move the files; a command line way to do it is:
mv ~/Schreibtisch/* ~/Desktop
When you have made sure that all the files were moved correctly, you can remove ~/Schreibtisch.