Taxes & so on...

Hi guys!
My name is Daniel, I'm kinda new in Warsaw (about 1.5 month), and also in the forum (about 1.5 week ).
I've been struggling slowly through the mazes of expat bureucracy, and now that I might have finally found a job that does not require a work permit (as a language teacher in a recognized institute...it's actually not a real job, more like a volunteering with costs of living covering), I need to go to get a tax number, and also some kind of declaration that I don't need to pay taxes in Poland. So I was told by the people in the organization for the foreigners...but I have no idea where this thing is, what is it exactly, and when is it open.

Any of you been there already, and knows how to help me? I'd appreciate it a lot, thanks!!
Oh, and in general feel free to get in touch, I'll be happy to get to know some fate-sharing colleagues