In this situation, can you stop the car immediately after this sign?

In the photo you are approaching a bridge with white and blue barriers, and on the right there is sign F-4 with the name of the river "Wisła" (the Vistula). Immediately beyond this sign, that is on the bridge, you do not have the right to stop the vehicle. The answer is: no.

The Road Traffic Act prohibits stopping a vehicle in a tunnel, on a bridge or on a flyover; the Regulation on road signs and signals states that sign F-4 gives the name of the river over which the road passes, and thus announces that you are entering a bridge. The bridge is narrow, without a shoulder, and the barriers do not let you pull over to the side, so a car standing on it blocks the lane and forces others to move into the opposite lane at a place with limited visibility. If you have to stop, you do it before the bridge or after it; if you break down on the bridge, you switch on the hazard warning lights and put out the warning triangle.

Legal basis: Art. 49 para. 1 point 3 of the Road Traffic Act (Prawo o ruchu drogowym); § 69 para. 4 of the Regulation on road signs and signals