Wooden staircase (Beech?) we do not like

Is it even possible to take the staircase apart?...

You would have to assess that yourself, and it would be your responsibility since you want to carry out the measure...

The staircase will be glued. For this, there are plug connections and individual mounting points in the staircase wall. So: I consider disassembling and reassembling to be unrealistic. Only: How is it supposed to look nice then? I can only advise against it – without disassembling, I think it will not look nice.

The other option is to hire a staircase builder, who can dismantle the staircase, work on it, and reassemble it.

Since we also didn't like beech wood and preferred dark wood, we sought advice from the staircase builder. Walnut was unaffordable for us. The alternative was then dark-stained beech. A wood expert will certainly notice that it is beech, but we like it because it no longer looks like ordinary beech. We had the staircase builder bring the same stain, because we stained beech boards in the same color tone, equipped them with LED lights, and then installed them as hallway lamps. However, the boards definitely do not look as evenly stained as the stair treads. So I would be cautious about doing it yourself, lest the staircase ends up looking worse than before.