Can the person riding the bicycle overtake the slowly-moving vehicles on their right?

Why?

Yes, a cyclist may overtake slow-moving vehicles on their right, except other bicycles. In the picture, the cyclist is to the right of the dark car, which is a permitted side for this manoeuvre. The cyclist must still exercise particular caution and leave a safe clearance.

art. 24 ust. 12 i ust. 2 Prawa o ruchu drogowym