Thanks!

After launching it, I cannot see the system partition. Only after selecting 'View all'.
After that, a message appears (translated from German): Handling non-SFS-partitions is dangerous.
I continued and then could select DH0.
Then I did choose 'Check Volume'.
- check root blocks
- Error: Could not read rootblock in block 0
- There are errors in the file system structure. It is recommended to back up the data and repair this partition.

Additionally a second windows appears: Error while checking the system. Block 10990838 invalid identifier

And now? How can I repair it? Choosing 'Scan volume'?