>>5603901deal with all of them and then you can focus on the black knight... if you don't want to fight him you can do it later anyways
the game is not that hard, you just don't know how to play it yet... after your first walktrough you'll feel the first half game as a piece of cake
by the way, focus on upgrading your weapons as soon as you can (except if it's drake sword), so you don't have a very hard time with some bosses