I want to add the following.
Yesterday during the day I could install and run everything, but because I want to start it from SSD I had to install it a lot of times.
The problems started in the evening. That is when the troubles began and I couldn't start OMV5 again.
So something happened during the day.
Now I will go back to OMV4. I still have the image and this is working.
It happend yesterday during the day. Anyone knows of changes to omv 5 that were made yesterday maybe ?