Floor levelling before or after hanging walls

Hi,
I’m doing a full renovation of an old house, and have had the old walls and flooring taken off in the two rooms which are on a concrete slab.

It appears as though the old concrete was done as one big lot of footings and separate slab poured in after.. this was done sometime in the 50’s I believe, and as you can imagine, the footings are now not straight, and the interior slab has come away from the footings and is not level at all, in one corner, the slab is sticking above the footing, and the rest of it is sitting below the footings. In some parts, the base of the old frame has gaps between it and the footings.. I have filled the gap between the footings and slab, and I have floor leveller ready to go..

My question is whether I level the floor before or after the plasterer comes to hang the walls ??