When Invem starts charging up after the three shots and starts flashing green you can either dash through and start shooting for some easy damage or you can jump over and do the same; either works. When you are able to survive to the phase when Invem throws down the four pillars you can use the dash into the pillars and heal which is what made the boss battle go from impossible to beatable within 3 tries for me. Finally listening to music will make it much easier, well not actually but your mental will be much better. Hope this helps ya if there is even anyone left trying to get all the achievements like me lol!