In this situation, are you allowed to overtake several vehicles at once?

Why?

Several vehicles are travelling in the right-hand lane, and you may overtake them in succession while remaining in the left-hand lane. You do not have to move into every gap between them if you are continuing to overtake without obstructing traffic. Return safely to the right-hand lane once you have finished.

art. 16 ust. 4 oraz art. 24 ust. 1 i 2 Prawa o ruchu drogowym