About problems with the Trinitarian interpretation of John 1:1-5. More info below.

Jesus expressed/declared the Father who is Light. (Jn 1:18; 1 Jn 1:5). Jesus tells you that the Father abiding in a man of flesh is who did the works. (Jn 14:10). The Word which this man of flesh declared was the Father (Jn 1:18), the Word he proclaimed was God the Father (Jn 1:1c). The Light which shined into the darkness was the Father as expressed through that flesh in word and deed. The True Light coming into the world was the Father who that flesh Jesus declared (1:18). God the Father proclaimed Himself and His will by means of that flesh named Jesus of Nazareth. The Word declared, expressed, proclaimed, was God, the Father.

Think about these things when you read John's "Prologue." The apostles referred to the beginning of Christianity, the beginning of the Gospel, as "the beginning" (see Mark 1:1; Luke 1:1-2; 1 John 1:1,5; 2:7, 14, 24). The word of God is something you proclaim in both word and deed. That's why Jesus said we are "the light of the world" (Matt 5:14) just as he said he is "the light of the world." God the Father is light (1 John 1:1-5) and the Father abiding in Jesus did the works (14:10; see Acts 2:22). In this way, Jesus proclaimed the Father so that we might know the Father and have life (John 14:4; 17:3; 1 Jn 5:20). This flesh expressed/proclaimed/declared the Father to the world (1:18). The Word Jesus expressed WAS God (1:1c), God the Father. God the Father shined His light by means of human flesh who denied himself to do the will of the Father. This is the Word John is talking about at 1:1-5, the declaration of the Father through human flesh, His only begotten Son.

In the beginning of the Gospel was the Word proclaimed by Jesus of Nazareth and the Word proclaimed was with God (in the bosom of the Father) and the Word proclaimed WAS God, God the Father who Jesus declared (1:18). The Word was with God in the beginning (in the bosom of the Father). Everything came to be through the Father's word and nothing came to be apart from His Word that has come to be. The Father's Word is the Bread of Life, and in doing His Word is life, and that life is the light of men. God the Father is light and He shined in the darkness of the world - the Father abiding in Jesus did the works (14:10). There was a man sent from God whose name was John. He came to testify about this Light which was coming into the world - the Father who was expressed/declared by human flesh: Jesus. The True Light, the Father who enlightens every man, was coming into the world. John came to prepare His way. He came to his own but His own did not receive Him. The Father who is Light shined in the darkness but the darkness did not receive Him. In this way, the Father was in the world and even though the world was made through Him, the world did not know Him. Jesus, man of flesh, came that we might know Him, the Father, who was declared by means of this man of flesh who denied himself and only did His Father's will. The Word became flesh because he kept his Father's Word. That fleshly Word declared the Father. The Word proclaimed/declared by that flesh WAS GOD, that is, God our Father.

This is easy to understand if you let go of your preconceptions. If you fully understand, you will also completely understand why John wrote the following:

By this you know the Spirit of God: every spirit that confesses that Jesus Christ has come in flesh is from God. 1 John 4:2.

He who eats my flesh and drinks my blood abides in me, and I in him. As the living Father sent me, and I live because of the Father, so he who eats me, he also will live because of me. John 6:56-57.

By this you know the Spirit of God: every spirit that confesses that Jesus Christ has come in flesh is from God. 1 John 4:2.

This is the one who came by water and blood, Jesus Christ; not in the water only, but in the water and in the blood. 1 John 5:6

By this you know the Spirit of God: every spirit that confesses that Jesus Christ has come in flesh is from God. 1 John 4:2.

We know that the son of God has come, and has given us understanding so that we may know the True One; and we are in the True One, in HIS son Jesus Christ. This is the True God and eternal life. Little children, guard yourselves from idols. 1 John 5:20-21.