DH bikes have forks at least twice if not three times as big as a cross country bike. More than likely if you read the manual on
your bike you will see it is not for DH. You might get away with it but you would have to be a lot more than a newbe and you will more than likely destroy the bike. Simply go to any LBS and ask to look at a DH bike and see what people are riding DH and compare it to what you have. You will get your answer yourself.