Hi,
first of all, this is the german board, so creating threads in german ist appreciated =)
Sounds like the partitiontype has changed. Why? dunno!
You can change it, but you have to know the original type and parameters.
But at first, I would try to save the data with an linux live stick.
You can change the type by opening powershell. Enter
->diskpart
->list disk
->select disk
->set id....
this is, how set id works
regards