Why is the gospel of Judah different then the new testament? who is lying?

There is no "gospel of Judah" as part of the accepted canon of Scripture. And if such a book exists, and if it is different from the New Testament (as your question points out), then you have your answer - it is not part of the New Testament because it is in disagreement, which can mean only one thing - the writings of Judah were either a fabrication (like a good "Harry Potter" book), specifically as entertaining fiction; or written to deliberately mislead and misguide people.