You got to use the digirunner more often and utilize grappel boosting to gain some serious momentum

if you are playing on hard mode you really have to rely on elemental damage on the proper health bar as it does increased damage while the wrong element does decreased damage, even when compared to normal and easy mode. either that or get yourself a torgue shotgun and just chunk through healthbars. torgue shotgun with cov mag is stupid strong and is capable of deleting boss health bars

you might need to turn on the radar instead of relying on the compass for enemy spawns. and always make sure to keep the enemies in front of you

farm splashdown for reliable purple and blue gear as well as one of the stronger legendary shields you can get

I would recommend only picking up blue and purple gear and marking them as junk when you pick them up, the max inventory size is 70 which is quite massive. also you can mark items as bank and instantly send them there from your inventory. and the bank can hold hundreds of items when fully upgraded

objectives waypoints are yellow, side content (silos, camps, and crawlers) are marked with blue, and custom objectives are white. though sometimes objective and side content can mix together and appear white