Every part of scripture from Genesis to Revelation is inspired by God (God breathed).
2 Timothy 3:16 NKJV
All Scripture is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness…
Scripture has no other purpose but to testify of Jesus Christ and His finished work.
John 5:38-39 NKJV
But you do not have His word abiding in you, because whom He sent, Him you do not believe. You search the Scriptures, for in them you think you have eternal life; and these are they which testify of Me.
Both the Old Testament and the New Testament point to Jesus. Jesus is hidden in “shadows” (symbols) in the Old Testament and He is revealed in the New Testament (Ephesians 3:3-5).