It is one thing not to understand it and quite another thing to deny it. It seems to me that you are saying you don't understand it.
The Scriptures do provide plenty, in fact overwhelming evidence of the Triune nature of God. It does grammatically. It does so by attributing the same non-communicable attributes that make God to be God equally to the Father and to the Son and to the Holy Spirit. It does so by direct address or explicitly calling the Son God and the Holy Spirit God rather than referring to al Three as "god's". It does so by claiming that the "Godhead" is revealed in creation and it is overwhelming revealed in Creation as this Creation is a Triunity in many different ways.
If we want to talk about "persons" we are obviously speaking of three distinct centers of consciousness that are co-eternal, co-equal and yet one is not the other and all three claim all attributes that belong to "one God."
The Scriptures does not teach "three beings" or "three gods" but one God who consists of three distinctions that cannot be confused with each other but are co-equal, co-eternal but stand in an orderly relationship to each other from Father to Son to Spirit in regard to position or rank. The very statement that God "is love" requires a trinity (1) A lover, (2) A beloved; (3) A spirit of love. The Biblical evidence is overwhelming and yet no human being is able to explain it fully.
One Creation but in Trinity - space, time and matter. Three different aspects but Take one aspect away and this present creation ceases to exist as it is.
Matter = energy, motion and phenomena. Three different aspects but Take one away and Matter ceases to exist
Time = past, present and future. Three different aspects but remove one and time ceases to exist.
Space = length, breadth and depth. Three different aspects but remove one and space ceases to exist.
The Godhead is revealed in Creation - Romans 1:20.