I checked the vb
-database itself. The pp_categories-table showed different attributes for the categories. The categories, which didnīt show up in admin-"Edit Categories" were present in this table, but had an entry "a" for cattype. All other categories, which behaved normally in both the admin-panel and within photopost-home, had the entry "c" in this cattype-field.
I changed the entries "a" to "c" in those categories and after playing around with the "Edit Categories"-option in the admin-panel the categories now are working as they should.
In the "Members Galleries"-category - which should have been empty, cause there is IMHO no equivalent in vbgallery - there were shown huge image-counts and post-counts too, but correctly no pics at all. Maybe a sum of all images and posts, I canīt remember the exact number. I set the lastpost-, lastphotos-, photos- and post-fields to zero and emptied "Members Galleries" in "Edit Categories".
Now everything seems to be fine. No pics and no posts are listed in the Members-Galleries-counts and all other categories are shown as they should.
Maybe the import was faulty in my case - but I canīt figure out any causes for it. Anyway, now it seems to be ok.