Phone phone cant reset due to edited build prop

hi everyone! I need ur heip. am using the Vodafone 858 smart / U8160. I rooted my phone and I edited the build prop for some time . A friend of mine deleted the super user installed and it deleted the unroot the phone.
right now, I can't re-root the phone and cannot reset the phone to it factory settings due to the build prop edit I made.
pls help me