After about 2 weeks some of the brown areas grew
lawn but others didn't so I still have a patchy lawn. Any one knows why this
happens and how to repair it ?

Sometimes lawn seed doesn't sprout (seed became dry after sowing) or sprouts
slowly (low temperatures). Re-sow the seed and see what happens.

If nothing comes up you might suspect that there is something toxic in spots.
Could be concentrations of salt? Or other chemicals?