How much does it cost to fix my lawn?

Hello. Recently my dad felt the need to rip grass off my lawn and try to replace it. as you can see he had no idea what he was doing. So my question how much would it cost to replace this grass. i plan on hiring on somebody else to do it but i would just like to have rough estimate. ive taken photos and its not my whole lawn just parts of it. Also would it cost to hire a gardener to do this and maybe add some flowers. thanks for the help