Hello, I am planning to travel by night train from Sofia to Istanbul, but according to information from the Bulgarian Railways, buying tickets is only possible at the international ticket office of the train station. So, is there any possibility to buy the tickets in advance since I don't plan to stay in Sofia (in the morning I will arrive and leave for Istanbul in the afternoon), and I am afraid that the tickets will be sold out on the day of the trip?
Thank you in advance,