A discussion in the scriptures with an apologetic.

"You cannot find the Trinity anywhere in the Bible because the concept did not exist during any period of the composition of the Bible

That is just a verse that mentions Spirit, water, and blood -- water and blood here referring to the death of Jesus as atonement for sin. Basically it's saying that the Holy Spirit, the blood of Christ, and the water of atonement, all testify in agreement.

The verse says nothing about the Father, Son, and Holy Spirit being three comaterial, coequal, co-divine persons. That is a level of theological specificity and sophistication that you will not find in the Bible, and which developed over centuries of followers reflecting back on the text and trying to figure out how it all fit in their minds. 

I mean, church doctrine holds that the author of 1 John also wrote the Gospel of John -- so why, in the Gospel of John, does Jesus say the Father is "greater than I" (John 14:28)? Seems a clear indication that the author of John did not consider Jesus and God coequal. 

Tl;dr, we read the Trinity into the text; it isn't actually there.

Here is a verse that mentions all three being one and in heaven.

1 John 5:7

There are three in heaven who prove it is true. [They are the Father, the Word, and the Holy Spirit. These three are one.]

Bro, this is literally the first verse you quoted, just from a poorer and less accurate translation.

The bits I put in brackets are called the Johannine Comma and if you want to read more about how it's not actually in the Bible, there's your linkydinky.

• It's absent from the earliest Greek manuscripts. Even the later ones are inconsistent about how it's phrased.
  
• A good indication that a passage has been interpolated, or inserted into the original manuscript, is when it appears at the bottom, top, or sides of a text instead of in the text, as it appears in this image (that's the Johannine Comma at the bottom).
  
• There's academic debate about whether Cyprian was quoting the Comma, but in any case he was writing in the third century, when Trinitarian ideology was already developing. And consider that other pro-Trinitarian patriarchs, like Athanasius, or Origen, who had every reason to appeal to the passage if they were aware of it, never did.
  
• Jerome didn't like that it was translated faithfully in other manuscripts because accurate translations undermined church doctrine. "Indeed, it has come to our notice that in this letter some unfaithful translators have gone far astray from the truth of the faith, for in their edition they provide just the words for three [witnesses]—namely water, blood and spirit—and omit the testimony of the Father, the Word and the Spirit, by which the Catholic faith is especially strengthened--" Because if it doesn't strengthen Catholic dogma, it must be wrong, right?
  
• Nah there's no grammatical problems with the original Greek.
  
• The Council of Carthage was in the fifth century, when Trinitarian ideology was coming to a peak. The church had decided what it wanted to believe and canonized it, regardless of what the text explicitly states; it's been doing that ever since.
  

• It's absent from the earliest Greek manuscripts. Even the later ones are inconsistent about how it's phrased.
  
• A good indication that a passage has been interpolated, or inserted into the original manuscript, is when it appears at the bottom, top, or sides of a text instead of in the text, as it appears in this image (that's the Johannine Comma at the bottom).
  
• There's academic debate about whether Cyprian was quoting the Comma, but in any case he was writing in the third century, when Trinitarian ideology was already developing. And consider that other pro-Trinitarian patriarchs, like Athanasius, or Origen, who had every reason to appeal to the passage if they were aware of it, never did.
  
• Jerome didn't like that it was translated faithfully in other manuscripts because accurate translations undermined church doctrine. "Indeed, it has come to our notice that in this letter some unfaithful translators have gone far astray from the truth of the faith, for in their edition they provide just the words for three [witnesses]—namely water, blood and spirit—and omit the testimony of the Father, the Word and the Spirit, by which the Catholic faith is especially strengthened--" Because if it doesn't strengthen Catholic dogma, it must be wrong, right?
  
• Nah there's no grammatical problems with the original Greek.
  
• The Council of Carthage was in the fifth century, when Trinitarian ideology was coming to a peak. The church had decided what it wanted to believe and canonized it, regardless of what the text explicitly states; it's been doing that ever since.
  

Tl;dr: The Johannine Comma is just so inconsistently attested to in the manuscripts that most translations of the Bible omit it as spurious. When a passage is original, it's usually copied in the same way, with the same phrasing, in the same place, by scribes. When it's not original, it moves around, appears in some texts but not others, and the phrasing varies. The evidence is pretty conclusive.

1. Coequal
   
2. Comaterial
   
3. Co-divine
   

John 10:30 I and my Father are one.

• John 17:20-23  My prayer is not for them alone. I pray also for those who will believe in me through their message, that all of them may be one, Father, just as you are in me and I am in you. May they also be in us so that the world may believe that you have sent me. I have given them the glory that you gave me, that they may be one as we are one— I in them and you in me—so that they may be brought to complete unity. Then the world will know that you sent me and have loved them even as you have loved me.
  

You can quote verses which identify the three parts of the Trinity all day. What you need are verses which identify the unique relationship between the parts. Namely, that they are each:

Coequal

Comaterial

Co-divine

Now you're just ignoring my counterarguments entirely. Like a basic biiiiAAAATCH.

Engage the content of my arguments vis-a-vis John 17:20-23 and 1 John 5:7 or gtfo.

Are you seriously just copying and pasting your responses from elsewhere like a two-bit bitch who can't connect neurons on his own. Where is your fucking pride, Shila.

Quoting scholars is one thing, copying and pasting the entirety of your response without inserting any words or arguments of your own is another. I might as well be debating Alexa ffs.