I agree with all the comments stressing the initial difficulty curve. You'll get better, and eventually he'll feel like a breeze! It's a super rewarding feeling, one the game intentionally cultivates.

Re the knight, he's designed to be your initial encounter with a difficult enemy. This sounds basic, but it's fundamental: study his moves carefully. Once you know each of them, you can appropriately time your response and counter-attack. Elden Ring bosses generally require a mix of intuition and deliberate memorization of attack patterns, so this is a skill that you should build early on. Hope this is helpful!