I know the game has changed since this video came out but damn that was clean. I lost my mind and finally killed him on my 30th attempt last night lol.
It's easy, when the boss gets his shield you have to get away from him until he makes the poison sphere, if you touch the sphere you die no matter what, it's not dodgeable, you have to get away from him. Once he makes the sphere, continue killing him in the same way, dodge and shoot.
Try uninstalling the game and deleting the last update, install the game as it came out on the first day and everything will be done perfectly. (I couldn't answer before, I'm sorry)
