Are you obliged in this situation to abide by the signal of the person directing the traffic?

At the junction, the traffic lights are working and showing you green, and at the same time a police officer directing traffic is standing there with his back to you (you can see his back). These two signals contradict each other, and in such a situation you must follow the police officer's instruction. So you must follow his body position and stop despite the green light.

The Road Traffic Act says that a road user must follow the instructions and signals of persons directing traffic, even if the rules, traffic light signals or signs indicate a different way of behaving, and the instructions of these persons take precedence over traffic light signals and signs. A police officer usually directs traffic when the traffic lights cannot cope with the situation - that is why he, and not the lights, decides who goes.

Legal basis: Art. 5 para. 1 and 2 of the Road Traffic Act (Prawo o ruchu drogowym); § 108 para. 3 of the Regulation on road signs and signals