How to manually delete blank categorie?

Because I'm working with huge amount of data, I tried to use categories to hide some data. My table looks like this: First there is a name of products, then we have the list of the products and last all the main products sums. Then another names of products and so on... The problem is that the only data that is needed to be categorised is the products list. But when i try to do that the rest of the date appears in a blank categorie. When I try to delete it all categories disappears. Any tips?

PS.: I could hide rows, but it is not confinient when you are working and analysing such information.