Hi what is quickest train to get to alexanderplatz from airport midday on a Saturday in may 25
Direct regional trains every 30 minutes at 14 and 44 past the hour taking 26 to 27 minutes, plus an S-Bahn at 49 past the hour taking 43 minutes. Options with connections at other times.
https://int.bahn.de/en
RE8 and RB23 are fastest - S9 has more stops.
I recommend to use this journey planner - it contains all means of transport and all actual constructions & disruptions.
https://sbahn.berlin/en/
Choose ABC fare for tickets. Ensure to time stamp paper tickets for validation before entering trains.
Avoid taxi or bus at this date: full closure of Autobahn part.