Parquet repaired after water damage

floating solid parquet flooring that is 30 years old? Sure?

Yes, we moved it shortly after we moved in.

But I think I misunderstood the term Massiv. So when I look at an edge of the floor, it is not "a board" but two or three layers. On top is maple.

Ok, then of course it doesn't work to chisel out individual pieces. Floating installation is always a problem, also when sanding. Have you asked a second parquet layer?