In this situation, when changing to the left lane, are you obliged to give the right of way to the vehicle in that lane?

Yes, this is one of the fundamental rules of the road. When changing lanes, you are joining a new stream of traffic, so you must give way to everyone already in that lane. According to Art. 22 para. 4 of the Road Traffic Act, the driver is obliged to give way to a vehicle driving in the lane they intend to enter.