It should be possible to temporarily disable this 3rd party search extension, then do what you want to do with the items or categories, and re-enable your search feature after that.
Try and go to Extensions > Manage > Manage, into the search field type
radius, click on the search icon, look for this component — it will be name "Geo Radius Search" or something similar — and disable it.
Try if you can access your categories now.
So it is possible to change the categories in the database directly? Can you tell me who I can find the special table ?
It is possible, but changes in the database are generally risky.
There is more than one table with ZOO content. It would very much depend on what precisely you want to change.
Do you want to move items to a different category? Do you want to change a category name or description?