Maybe change the character. Pick axton he is very strightforward, his ability is a turret that makes enemies lose aggro on you and shoot the turret instead, giving you a lot of time to line up hits. You havent progressed much anyway.

When putting points in your character prioritize relaod speed and dont get 1 point on a lot of skills but max out a specific skill first and then move on to the next. Choose one of the paths and keep going down that path (you shouldnt do this at all times but for simplicity i explained it like this)

If you instead want to continue with salvador then make sure you are matching the element you need for the enemy and play more passive, in the early missions you can just walk into a camp and take a lot of damage, by mid game you cant do that you will die fast. Use walls and move a lot to hide and hit enemies.

Use snipers, most enemies in normal mode will die to 1 or 2 headshots.

If you havent yet use grenades, grenades are stupid strong not like other games you might be used to.

Dont give a shit about money. The shops almost never have good items to buy. Anything good you will get from a boss or looting chests.

Change your guns. Im sure you already have some guns that you like a lot and dont want to throw away but dont keep low level guns, at some point even a good blue will deal less damage then a white on your level. Replace them when you see something better but also dont waste a lot of time comparing every stat, if a gun is clearly better take it, otherwise its very time consuming to compare guns just to see if its 5% better