What's up with stupid "look around for battery" puzzle and this weird fight with vortigaunts while being ♥♥♥♥♥♥♥ poisoned? (and there is also nothing explaining why i got poisoned, what is going on?)

he is legit annoying to play as in ez2

I've got a lot of different questions coming at me from a lot of different places. It's going to be easier for me to answer your lore/development questions under one thread, so ask me stuff in here. If you're having issues, please use the troubleshooting and bugs forum. Keep it civil....

None of what I did while playing in offline mode counted towards achievements... :(

In the big room with pilars, after several attempts i managed to destroy the 3 energy balls and dodge the laser beams coming from the center but after that i can't defeat the vortigaunt no matter what i throw to him it won't die... Also the air is poison and it kills me slowly, wasted all health and armor stations triyng to stay alive but no luck... Any clue how to defeat it?...