Complex sentence: Although none of the categories are independent, and many camps could be classified as a mixture of several of the above, and all camps had some of the elements of an extermination camp, systematic extermination of new-arrivals occurred in very specific camps.
Split into simpler sentences: Although none of the categories are independent, many camps could be classified as a mixture of several of the above. All camps had some of the elements of an extermination camp, but systematic extermination of new-arrivals occurred in very specific camps.