Taxes to pay on B2B contract in Poland?

Cheers guys,

I am Ukrainian living in Poland but working offshore in Europe with permanent contract, recently I have received the same position but in Polish waters from Polish company but the requirement is that I need to open a one person company or as I understood from internet “JDG” as the contract this company offers is b2b.

The salary before taxes is 8400 eur.

How much I will have on hand after all taxes will be paid including NFZ, social security etc.. should I also pay to ZUS?

The reason I am asking here because AI tools all give different info ranging from 5800 to 6800 despite the fact I change nothing from my request. The only attractive what does sound to me that on B2B I loose less money rather than when it’s paid by my employer directly.

Appreciate your wish to assist!