Problems with the stairs (concrete/wood)

Hello dear forum,

There are problems with our staircase (concrete/wood). Either it was installed incorrectly or the walls by the staircase are too short.

1. Both walls are not the same (see picture). The shorter side can be made equal with 2 drywall panels. After plastering, you won't see any difference.

2. Nevertheless, both walls are too short. The wooden tread is 4 cm longer than the concrete step, the wall is only 2 cm longer. You really can't shorten it because there will be a riser under the tread. This is just under 2 cm thick.

The stair builder’s idea is simply to make the riser a bit wider and pull it in front of the wall. But I’m not really happy with that.

Couldn’t you just use a drywall panel at the bottom instead of the riser, paint/ plaster it white, and make the treads shorter that way…?

Do you have any ideas?

Attached is also a picture of how I originally wanted it…

Unfortunately opened twice, please delete here. Thank you