Hello Nikos21Gr
If you travel on Friday/Saturday or Saturday/Sunday nights, the station is certainly open because you have night trains on weekends, also before a holiday.
Nikos21Gr I can’t understand why they are selling tickets like that when you don’t have the option to stay in the station and wait.
Some people who buy such tickets can have accommodation to sleep and don’t stay in the station.
Kind regards
Danhiel