I've not seem the dubbed version, so I've no idea what's been cut. I have the English sub-titled Australian release, and it is 135 minutes, so three minutes have been cut.
Not having seen any other version, I can only guess why.
The scene where Christiane and Detlef have sex seems to have been edited as it cuts between different shots very awkwardly. I'd say this would have been done so it could get the "R" certificate to be released instead of being refused classification, and so not be able to be released, because under the guidelines it could have been deemed child pornography.
Bear in mind that quoted running times are often inexact, and are therefore not a reliable guide as to whether, and to what extent, a film has been censored. Also remember that the differing frame rates between the PAL (Europe/Australia) and NTSC (North America) releases will result a running time difference of several minutes.
My old VHS english-dubbed video is from 1986 (picked up at local UK flea-market for a couple of english pounds) and says 120mins approx. Im thinkimng of replacing with updated DVD though. Jan B