The Bible teach that there is One God. To some One God means One Being but the Bible described One God expressed or represented by Father, Son, and the Holy Spirit commonly called Trinity or Three Persons in One God.
The three are all present in creation, in salvation of mankind etc.. In the Old Testament deeper reading reveals the presence of God, the Father, the pre incarnate Christ and the Spirit.
Since this blog is short it is impossible to cover or even explain Trinity. But my main basis for Trinty is our Lord Jesus Christ. He calls on the Father and also said that when He goes back to heaven , the Holy Spirit will come to reside in believers.
Some may say but there are three Persons or three Beings therefore three gods. But consider there is no rivalry between the three, therefore total cooperation. Total unity.
Maybe in the future when we see God everything will be clarified.