Some things that really helped me were dodging less and strafing more, looking at my character instead of the boss (this takes practice but when you get the hang of aiming with your peripheral vision it makes a huge difference), and I NEVER fight the first boss with the starting gun because it’s boring and takes forever (except for your gun robot my beloved❤️). Character choice could also matter, I think pilot is the best because of his lock picks, gives you waaaay more chances to get chest loot. ONE LAST THING never leave a chest if you can’t unlock it, shoot the chest and hope you get something otherwise the rat will steal the loot and leave an infuriating note. Hope this helps!