What does this traffic sign mean?

You answered everything correctly. This traffic sign shows a St. Andrew's cross with an additional symbol for electrical danger, indicating a railway crossing with overhead electrical wires. It means there are electrical wires above, rail traffic always has priority, and you must always wait when a rail vehicle is approaching. Always pay attention to such signs, stop when a train is coming, and be aware of electrical hazards. This helps prevent accidents and ensures everyone's safety at rail crossings.