In this situation, are you allowed to continue driving in the middle lane?

In the video you are driving in the middle lane of a three-lane expressway; on the right, the right lane turns into an exit lane with an arrow pointing right painted on it, and a flyover crosses above the road. You are allowed to continue in the middle lane. The answer is: yes.

The Road Traffic Act requires a driver to drive as close as possible to the right edge of the roadway, but this rule refers to lanes intended for driving in your direction. Before the interchange, the right lane has become a deceleration lane: the arrow on the roadway shows that it leads to the exit, not further along the expressway. If you moved into it, you would have to return to the middle lane straight away, cutting across the path of vehicles that are just getting into position to exit - this is dangerous and pointless. So for drivers going straight on, the lane "for driving" closest to the right edge is the middle lane, and you continue in it. Before every interchange you read the arrows and the signs above the roadway and stay in the lane that leads in your direction. After passing the interchange, when the right lane is again a lane for going straight on and is free, you return to it.

Legal basis: Art. 16 para. 4 of the Road Traffic Act (Prawo o ruchu drogowym); § 87 para. 1 of the Regulation on road signs and signals