Removing the concrete from the top off a concrete column
You almost certainly do NOT want to cut off the rebar in the columns as suggested by @EdBeal - that should be tied in and/or bent and tied in to the rebar in the beam.

I'd think long and hard about just raising the upper floor by another 40 cm rather than chiseling all those columns - but if they are freshly poured, you may find that they will chisel easily, as the green concrete is still going to be relatively weak.