My former house had front yard issues, I round up killed the entire lawn, tilled it, leveled it, let it sit for a month, and round up killed everything a second time, tilled again, leveled it, then rented a big heavy roller thing to make the dirt level and smooth by crushing all the dirt chunks into a smooth surface.
I then hired a hydro spray guy and had him spray the lawn on, and within 3 weeks I had a good base and just filled in the thin spots with the same seed he used. Within a month and a half I had a choice yard that was the envy of the neighborhood.