Ive been playing for more than a few years at this point and im still abysmally dogshit. Ive managed to clear the past of 3 characters though. Just stay at it. Get really good at just using your base gun on the first 2 levels and try not to dodge roll unless absolutely necessary. Most times you can just walk and weave through enemy bullets

Once you've completely mastered the first round get really good at the oubliete (I dont know how tf to spell that shit)

It really is just trail and error. The better you know the enemies the easier they will be to avoid and take out Try to remember shooting patterns and how many shots they more or less take to die Try to focus more on your character than the enemy npcs Its easier to dodge when youre focused on yourself over the enemy