God is One God (Deuteronomy 6:4) manifested in three ways:
The Father - the Most high, eternal, the Creator
Jesus - the Word (John 1:1-18), the Temple (Colossians 2:9, John 2:18-22), the Messiah
The Holy Spirit - the breath of God (Ruach HaKodesh), the power/Spirit that lives in those who have received Him.
When Paul said all scriptures are inspired by God (2 Timothy 3:16), he was referring to the Old Testament scriptures. HOWEVER, we believe the New Testament scriptures bear testimony to, and are the fulfillment of, the Old Testament. Therefore, we see the New Testament as being equally inspired by God. Having said that, the Old Testament is equally important and relevant today as is the New Testament.
The church is the continual manifest presence of Jesus on this earth. Before He left this earth, He instructed us to do even greater things than He did so that we can be light in the darkness. We are called to be His witnesses, being conformed and transformed into His likeness for His glory.