Is "dobrych przyjaciół" genitive or accusitive plural? Does the "of" indicate possession, making it genitive? .
why is "i have a good group of friends" marked as incorrect?
Why is 'good friends' in the genitive case here? I thought that the genitive case was used for negative sentences, after certain prepositions and to indicate possession. In this example, what exactly do the 'good friends' possess that puts them into the genitive case?
If anything, then something would have to possess them (okay, sounds like a need for exorcisms) for it to be Genitive.
The answer is "of". If you have 'of', it will (almost?) always be Genitive.
It is called a partitive genitive. It is used for phrases that require "of" to complete the meaning of a word consisting of "parts." e.g. part of, piece of, half of, group of, mass of, bag of, handful of, etc.