A Plural-- yet --Monotheistic God

"Monotheism (the belief in one deity) was unique to God’s people in the Old Testament. Moses said, “Hear, O Israel! The Lord is our God, the Lord is one!” (Deuteronomy 6:4).
The New Testament plainly teaches that there is one God. Paul described the idols as “so-called gods” because “there is no such thing as an idol in the world, and that there is no God but one”
(1 Corinthians 8:4-5).

While the Scriptures are clear that there is one God, they also describe three persons of God.
The Father, Son, and Holy Spirit are each referred to as “God” in the New Testament.

The Father is God –
“For when He received honor and glory from God the Father, such an utterance as this was made to Him by the Majestic

Glory, ‘This is My beloved Son with whom I am well-pleased’” 

(2 Peter 1:17).
The Son (Jesus) is God –
“But of the Son He says, ‘Your throne, O God, is forever and ever, and the righteous scepter is the scepter of His kingdom” (Hebrews 1:8).
The Holy Spirit is God –
“But Peter said, ‘Ananias, why has Satan filled your heart to lie to the Holy Spirit and to keep back some of the price of land? […] You have not lied to men but to God’” (Acts 5:3-4).

Though we do not find the term “Trinity” being used in the Bible, we can see from the passages above that the Father, the Son, and the Holy Spirit are all God."
PlainBible