Shall i Plead guilty or not guilty?? Please dont answer unless you have experience or some knowledge on law?

No, you have it all wrong. Prosecutors don't offer a deal because they have a weak case. They offer a deal because they have a good case and don't want to waste time in court. If your friend makes them go to court they'll be pissed and make sure he's prosecuted for it all and push for the highest sentence.