Is it prohibited in this situation to enter the roadway beyond this vertical sign?

In the video you are driving along a street next to a park; on the right there is a round red sign with a white horizontal bar - B-2 "no entry" - placed in front of the roadway to the right of an area closed to traffic, marked with white diagonal stripes; dark cars are coming towards you along that roadway - it is intended for traffic in the opposite direction. Beyond this sign, entering that roadway is prohibited. The answer is: yes.

The Regulation on road signs and signals states that sign B-2 "no entry" means that vehicles are prohibited from entering the road or roadway from the side where the sign is placed; a plate placed under it may exempt certain vehicles from the prohibition, but there is no such plate here. Sign B-2 stands at the exit end of a one-way roadway: from the other side, vehicles enter it at sign D-3, and entering from the B-2 side would mean driving against the traffic, straight towards drivers who do not expect anyone coming from the opposite direction. The prohibition is absolute and does not depend on whether anyone is driving along that roadway at the moment. You continue along your own roadway, on the left side of the area closed to traffic.

Legal basis: § 17 para. 1 of the Regulation on road signs and signals; Art. 5 para. 1 of the Road Traffic Act (Prawo o ruchu drogowym)