Is it possible to lower the floor structure?

How much can the screed be ground down if I only replace the floor covering with a thicker one that has better impact sound insulation?

You want to do that on the ground floor, right? You don't need any at all, since you're not disturbing anyone in the basement. I don't understand the intention. By the way, the biggest effect comes from the "insulation" under the screed. Normally, it serves not only for insulation but also for impact sound insulation. The floor covering was also glued. That fits. You won't be able to achieve anything more there.

One should perhaps also consider floor-to-ceiling windows and the entrance door when lowering the floor.

Why exactly are the 2.46m now a problem searching for a solution?

Because 2.46m are anything but en vogue, and many home builders advertise 2.7-2.8m as an expression of freedom and luxury.
If there were 15-20cm more here, one could still think about it.
But because realistically maybe 5cm, it is nonsense.

Then you just have to send the chandelier back, as stupid as that is.