What is Galatians chapter 3 verse 28?

That verse is saying that the Law shows us that we fail the Law, that we can't live up to it. "For all have sinned, and fall short of the glory of God."

There's a saying that when you're witnessing to someone you have to get them lost before you get them saved. In other Words, they have to realize that they fail, and don't live up to the commandments.