In this situation, given the obligation to give way to vehicles on the right, must you stop before the STOP sign and then before the stop line?

Why?

The B-20 stop sign requires you to stop at the designated place, which here is the visible stop line. You do not have to make separate stops before the sign and then before the line. Before entering, you must give way to the car travelling on the priority road.

§ 21 ust. 1 i 2 rozporządzenia w sprawie znaków i sygnałów drogowych