Are you obliged in this situation to make sure that there is no train coming from either side?

You are approaching a level crossing equipped with barriers, which are raised. Raised barriers do not exempt you from the duty to check whether a train is coming - the devices can break down, and visibility is sometimes limited. Before entering the tracks, you make sure yourself that nothing is coming from either side.

The Road Traffic Act says directly: a driver approaching a level crossing and driving over it exercises particular caution, and before entering the tracks is obliged to make sure that no rail vehicle is approaching. You drive at a speed that lets you stop in a safe place if a train does come or the barriers start to go down.

Legal basis: Art. 28 para. 1 and 2 of the Road Traffic Act (Prawo o ruchu drogowym)