When we use UFraw or other programs based on DCRAW we get the original picture, not the edited one.
When our photograffer takes a picture in DNG. Afterwards edits on this picture are done with photoshop or Lightroom. Picture is saved again in DNG.
When I open the picture the new picture in UFRaw I see the original picture.
How can I avoid this
You cannot. The edits in Lightroom are not done on the source image but saved as editing steps in the XMP (non-destructive editing). You could read the XMP-data but it won't help you, since you cannot re-apply the LR editing steps.
If you want to work on the edited picture, you will have to ask your photographer to export a TIFF from LR and use that instead of the DNG.