This boss is gonna test you for sure.
And its also gonna check you if you got any of the upgrades and new weapons.
If you don't this boss is almost impossible specially with just your first gun.
But since I am a gamer myself I now push you in the way of unlocking the Railgun or you go and find the hidden levels and do the challenges.
Or you farm up the gems.
Try the boss again and you will see he is really easy once you know the tricks of him.
And the last boss has a blind spot if you double jump and jetpack at his armpit level you can damage him
Good luck