Can mangled concrete floor be fixed?
a) Grind concrete until it is flat, then grout the remaining cracks.  You'll have an even thinner but flat floor, problem will likely re-occur.

or

b) Pour thicker new concrete over the top, with steel mesh, to make a more resilient replacement floor.  Might still crack, as base is suspect.

or

c) Cut out &amp; remove the failed floor, inspect the base to determine true cause, remove failed layers, install proper bedding, insulation layer &amp; damp proof membrane, re-pour concrete.