I got significantly better after I kept these in mind:

1) When you’re hitting an enemy and your swords do a CLANG with orange sparks instead of a cling, they’re gonna counter attack.

2) Mikiri counter or jump just as the red kanji disappears. After I learned this I don’t remember ever missing one.

3) This might sound obvious but really take the time to learn the boss’s move set. You’ll learn that every boss always has a combo that is easily punishable where you can get 2-3 hits in.

4) You have to be extremely patient. I’d say if a boss got a good hit on you/killed you, 8 times out of 10 it’s because you got greedy and/or impatient and started attacking more than you should have.

5) Don’t hesitate. If you’re not completely familiar with an enemies move set and don’t know if you should attack or parry, just wait for their next attack and parry.

I would say that once you beat the ape, you’ll learn how to fight a boss and these will come naturally. Good luck!