One God

Deut 6:4
Hear, O Israel: The LORD our God is one LORD:
KJV

The Hebrew word for "one" is echad;
'echad (ekh-awd'); a numeral from OT:258; properly, united, i.e. one; or (as an ordinal) first:

John 1:1-2
In the beginning was the Word, and the Word was with God, and the Word was God. 2 He was in the beginning with God.
NKJV

John 10:30
(Jesus said) I and My Father are one."
NKJV

Rom 3:29-31
Or is He the God of the Jews only? Is He not also the God of the Gentiles? Yes, of the Gentiles also, 30 since there is one God who will justify the circumcised by faith and the uncircumcised through faith.
NKJV

Rom 3:29-31
Or is He the God of the Jews only? Is He not also the God of the Gentiles? Yes, of the Gentiles also, 30 since there is one God who will justify the circumcised by faith and the uncircumcised through faith.
NKJV

1 Cor 8:6
.... yet for us there is one God, the Father, of whom are all things, and we for Him; and one Lord Jesus Christ, through whom are all things, and through whom we live.
NKJV

Eph 4:4-6
There is one body and one Spirit, just as you were called in one hope of your calling; 5 one Lord, one faith, one baptism; 6 one God and Father of all, who is above all, and through all, and in you all.
NKJV

1 Cor 15:27-28
For he "has put everything under his feet." Now when it says that "everything" has been put under him, it is clear that this does not include God himself, who put everything under Christ. 28 When he has done this, then the Son himself will be made subject to him who put everything under him, so that God may be all in all.
NIV

1 Cor 11:3
But I want you to know that the head of every man is Christ, the head of woman is man, and the head of Christ is God.
NKJV

1 John 5:7
For there are three that bear witness in heaven: the Father, the Word, and the Holy Spirit; and these three are one.
NKJV

1 Tim 2:5-6
For there is one God and one Mediator between God and men, the Man Christ Jesus, 6 who gave Himself a ransom for all, to be testified in due time
NKJV

There is much debate on the idea of One God. Is Yahweh God and Yeshua (Jesus) the Son of God? Or does Jesus have equal "headship" as Father God? Bear in mind that the term "trinity" is a Church term and not a biblical term. I do not believe that makes them wrong to use that term. It is simply how the Church views the position of Jesus as equal with God.
Based on John 1:1, Jesus (the word) is God in the flesh. And in John 10:30 Jesus says that he and the father are one. But in 1 Cor 11:3, the head of Christ is God.
Bear in mind that when Jesus said that he and the father are "one", I believe that he is using the word 'echad' as defined above. Also bear in mind that in Deut 6:4 above, when you see the word God, the hebrew word is Elohiym. Note that "Elohiym" is plural, more than one.

OT:430 'elohiym (el-o-heem'); plural of OT:433; gods in the ordinary sense; but specifically used (in the plural thus, especially with the article) of the supreme God;
OT:433 'elowahh (el-o'-ah; rarely (shortened) 'eloahh (el-o'-ah); probably prolonged (emphat.) from OT:410; a deity or the Deity:

So to put this in as simple of a statement as I see it,
There is more than one "God" (Elohiym; 'elowah or "el" is singular). So, though Jesus is not "Father God", he is "God the Son".
They are "one" in the way that they are united ('echad).
Jesus, as well as the spirit of God (Holy Spirit) was with Yahweh from the beginning and Yahweh is over all, 1 Cor 11:3.