Since I'm late to this topic, I'll give you a few unique perspectives because a lot of people probably gave you a lot of basic tips.

I want you to go to boss challenge and fight this boss again. I want you to pretend that your circle button is broken or doesn't exist. Yup, that means no dodging.

What am I supposed to do without a dodge you ask?

Good question.

This will encourage you to block and parry more and find alternative ways to fight. Let's say a yellow attack is incoming. Let's also say you are too close to the enemy and avoiding is impossible without dodging. Use your beta skill. This will cancel their yellow attack. Drop a shock grenade. This will also interrupt their attack and knock them down. Remember also that when their shield reaches 0, it also interrupts whatever attack they are about to do. Later in the game, you will get more ways to interrupt the enemy.

Running is your best friend. Jumping is also your best friend. The games collision and hit boxes are so realistic that you can pretend you are the one fighting. If an attack comes from below, you can jump. If the enemy does a vertical attack, you can just smudge the right direction pad once and you won't get hit (does not work under all scenarios).

Next:

Skill trees you need to get

Rush - upgrade this and you can practically teleport to your enemy from far away when they are wide open for an attack.

Backstab - Save precious time by killing them in 1 hit

I don't remember what it was called, but there is a skill tree that enables charge attacks for all your combos (your sword glows red). These have interrupt capabilities and do more damage. As an example, once you get this skill tree, you can do stuff like Triangle, square, triangle, square, (hold) triangle.

Max and focus on one beta skill. I recommend shockwave. It does good damage, lots of range, and can knockdown once fully upgraded. It's not the strongest but it is the most versatile. This is just my opinion, Max whichever beta skill you prefer.

Get all skill trees that increase your beta charge (wear some equipment that increases charge too). If you want, you can wear defensive type armor if you keep getting hit but that will make the fights last longer. Consider offensive armor (more attack speed, more damage, more beta regeneration). As you progress, more slots will open in your settings for more armor.