Confirm whether the problem is BVG, S-Bahn or a wider VBB issue before changing the whole day.
Best move: make central Berlin the plan
Walk the city that is already near you
If you are already around Alexanderplatz or Museum Island and the day is flexible, stop forcing the same train. Walk west, keep the official app open, and rejoin transport from a calmer hub.
Route that still works
If the centre is close, start walking toward Museum Island or Hackescher Markt instead of waiting through three bad signs.
Use a working rail layer to a nearby hub, then walk, bike, scooter or taxi for the awkward final part.