Stuck on Belial Boss

So I have been stuck on Belial for a couple months now (been playing on and off recently at this point). I’ve used multiple YouTube videos and found that using the gun at the beginning is best I got really close with that but I’m out of money in game now not sure what to do and how to get more at this pine In the space center area. Should I go to the story mode or keep trying atp in normal as I made it this far in Normal mode. Any advice would be appreciated.