What does the verse at Romans 3:4 mean?

This is the content of Romans 3:4 in the King James Authorized Version 1611: God forbid: yea, let God be true, but every man a liar; as it is written, That thou mightest be justified in thy sayings, and mightest overcome when thou art judged. Personally, if I found out that a teaching isn't based on God's Word the Bible, then I have all the reason to reject as mere man's opinion. In my days of old when I have a religion but not a relationship with Jesus Christ, I just ignore or accept anything I hear about the teachings of a church. Now that I have grown up by God's grace, I learned to be like the Bereans who search the Scripture daily if what Paul is saying is true based on the Scriptures.