Could Hamburg’s main train station be expanded underground?

Problem: Hamburg Central Station lacks capacity, with too few platforms and tracks, resulting in trains often having to wait outside the station and not being able to enter. In some cases, connections cannot be served because Hamburg Central Station lacks the necessary capacity. In addition, Hamburg Central Station is the busiest central station in Germany….

How safe is it at night in Hamburg for a woman with two children? What are the bus connections like?

My ex-husband arranged for the children and me to attend the theater “Harry Potter and the Cursed Child” and stay in a hotel right next to the main train station. We would arrive there by train that same day, check in, and then probably walk to the theater. I mean it all very kindly, but…