Can you put a top soil on lawn and lay another lawn?

Yes you can but the job is never satisfactory. You are better to kill off the existing sod and cultivate the ground rake it out level firm it and lay your turf, that is if you want a half decent job. Make sure that if you use a chemical to kill the existing sod that it will not affect the new grass that you replant. Possibly easier in the long run to dig up the existing sod and throw it away as you are cultivating the ground. Sod needs good root to soil contact so the roots have something to grow into. If layed on top of other vegetation the roots have nothing to take a hold in. A better way to remove the existing vegetation is to rent a sod cutter and compost the material removed. In a year or two it will be great for your garden or other compost needs. The sod cutter also leaves the ground almost perfectly flat to lay sod on.