Hello Stockfisch
Please choose english the next time you start a thread. Many of the users in here who might be able to help don't speak german. So the chance for getting your problem solved decreases.
But I guess it will be solved.... CvH ^^....your turn, I guess 
It could work - depends
1. make backup (really)
2. install tvh42 and disable it
3. copy content from /storage/.kodi/userdata/addon_data/service.multimedia.tvheadend/ to /storage/.kodi/userdata/addon_data/service.tvheadend42/
But drop config, epgdb and settings xml in the top folder - these files are better to keep from the 42 install.
4. activate tvh again pray that it works
Clean and working solution - new install 
Most important for me is to not lose the meta data of my recordings!
you can also try only to copy the recordics folder and drop the settigns and stuff - you have to try what works for you
