Are you allowed to make a U-turn at the intersection in this situation?

In the video you are waiting before a junction in town, and directional traffic lights S-3 at the left edge, after red and amber, show a green signal with two arrows: to the left and for a U-turn. So you are allowed to make a U-turn at this junction. The answer is: yes.

The Regulation on road signs and signals states that the signals of directional traffic lights S-3 apply to drivers travelling in the directions shown by the arrow or arrows, and the green signal of these traffic lights means that when driving in the direction shown there is no collision with other road users. The left arrow on S-3 alone would not allow a U-turn - only the additional U-turn arrow gives you this right. The Road Traffic Act prohibits U-turns in conditions where they could endanger safety or obstruct traffic, so you make the U-turn smoothly, from the left lane, making sure that nobody is entering on red.

Legal basis: § 97 para. 1 and 3 of the Regulation on road signs and signals; Art. 22 para. 6 point 4 of the Road Traffic Act (Prawo o ruchu drogowym)