Sigmili, welcome to the forum! 
There is no stupid questions or any reason to feel stupid, because this is unreal to know absolutely everything
. Do you remember - "no single character can handle every situation..."?
Anyway, petrification can be a difficult problem if you have not proper protection scrolls with you, but you can always go to the nearest merchant, buy the scrolls and return to the location where your poor petrified comrade stands - he won't go anywhere, so free him when you please
.
Good luck!
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Tanda,
with best regards from Guild of Assassins