I will be in Burgas on 20th April 2018 and I woluld like to go to Istambul, there is any train connection, how can I get there?
The only train from Bulgaria to Istanbul is Sofia Express, departing every evening from Sofia to Istanbul.
For catching Sofia Express, you can travel from Burgas to Sofia by train. Or you can get to Dimitrovgrad (which is closer), spend the day there and get to Sofia Express at midnight. Please check the train services at Bulgaria via BDZ.