Playing this game for the first time

Run up the stairs and jump attack him.

Get off here and keep trying user! You can do it!

dodge rather than block
parry and backstabs are broken

It takes some time until it clicks but after that it will get easier. Don't worry about dying. especially if you are used to faster faced games, the roll timing in Dark Souls 1 takes some time to get used to as everything is super telegraphed but also slow which can be misleading

dont fat roll

Your shield blocks one hundred percent of the damage he does, dude. Just be careful and only attack when you know you'll have enough stamina left to block. Keep your shield down when you can to recover stamina more quickly.

Don't worry. Learn his patterns, watch your stamina and roll whe you have to.
I'm playing DaS 3 and I killed Nameless King a couple hours ago after 3 days trying. You will eventually make it.

I beat the game 4 times and never parried.

Naked two handed iframing is the only proper way to play through dark soul.

Dying is part of the game, you're doing fine so long as you learn to adapt. Like others said, dodge/roll rather than try to tank damage.

In Dark Souls, you only really lose if you give up. You can do this.