OK, It takes some time to do the restoration of the scanned documents manually, but it is to overcome.
A very strange situation occurs while doing this.
I have introduced 3 Categories. All 3 are shown in the Documents, including the Category name. However 2 Categories I can find by searching to the name of the Category, the third Category shows no results. Searching for the common part in the document names, delivers them all. So the name of the third Category seems problematic.