Is it forbidden to park the car immediately after the countdown post you see here?

The countdown marker with one stripe (G-1c) visible on the right marks the zone directly before a level crossing. According to Art. 49 para. 2 pt. 3 of the Road Traffic Act, parking a vehicle is prohibited before and after a railway crossing, on both sides of the road, in the section from the crossing to this marker. This means that parking is not allowed in the area past this sign.