This all gets confusing when we plant ourselves on one side or the other side of the fence of whether or not the trinity or Triune God are either separate or one. But this is not the Scriptures description either way, They are both distinctly one, and yet always corporately one..and this is where our human brain goes... "what?" And we start to infer meanings of the Scriptural texts to reason it out.
According to the Bible, God is uniquely one (Deut. 6:4; 1 Cor. 8:6), yet He is also the Father, the Son, and the Spirit (Matt. 28:19b). This is difficult for the human mind to reconcile or explain, but this is the revelation in the Bible. Any attempt to reconcile these two aspects will only result in confusion. We should simply say that God is one and He is also three. He is the unique God, and He is the Father, Son, and Spirit. The three of the Divine Trinity are distinct, but not separate. They are distinctly three, yet they are also one.
The Father, the Son, and the Spirit coexist with one another (Matt. 3:16-17; Eph. 3:14-17), and They also exist permanently and inseperately with one another as yet being distinctly known. To coexist means to exist together at the same time. To understand the coexistence of the three of the Divine Trinity is not difficult, but to understand how the three of the Divine Trinity co-inhere is very difficult. To co-inhere means that the three of the Divine Trinity exist within one another, abide in each other (John 14:10-11; 17:21). The three of the Divine Trinity from eternity past have been and still are coexisting and coinhering with one another. One day the Second of the Divine Trinity, the Son, came to be a man through incarnation. He came from the Father, with the Father, and in the Father's name (John 8:29; 16:28a, 32b; 10:25). His coming with the Father was also by the Spirit (Matt. 1:20; Luke 1:35; 4:1).
This shows the coexistence of the three of the Divine Trinity in the incarnation. In John 14 the Son said that He was in the Father and the Father was in Him and that the words He spoke were not His own words but the Father's words (vv. 10, 24). This chapter also reveals that the Spirit of reality comes as the Son with the Father (vv. 16-20, 23, 26). This indicates the co-inherence of the three of the Divine Trinity. The Son lives in the Father and the Father lives in the Son; the Son's speaking is the Father's work.Another portion of the Word which reveals the co-inherence of the Divine Trinity is (Isaiah 9:6). In this verse the Son is called the Eternal Father. The child born, who is also the son given, is called the Wonderful Counselor, the Mighty God, the Eternal Father, and the Prince of Peace. The child who is the only begotten Son (John 3:16) is called the Mighty God. The son who is given is called the Eternal Father.
Although we cannot fully understand these portions of the Word, we have to accept the clear word of the Scriptures.
The three of the Divine Trinity are distinctly three and yet one. The Father is distinct from the Son, the Son is distinct from the Spirit, and the Spirit is distinct from the Father and the Son. Yet the Son is the Father (Isa. 9:6; John 14:9-10), and the Son is also the Spirit (2 Cor. 3:17). The Son became flesh (John 1:1, 14) and was called the last Adam. This last Adam through death and resurrection became a life-giving Spirit (1 Cor. 15:45b). The son given was called the Eternal Father, and after His death and resurrection He became the life-giving Spirit. Therefore, the Son is both the Father and the Spirit.
This is not simple, but it is true based on the Scriptures teachings.