Is God One ? Is God Trinity ? This concept is one if not the hardest to explain or understand. Perhaps you experienced a discussion about the essence of God. Some claims that belief in Trinity is a belief in three Gods.
The Bible teach there is One God but the Bible also teach that God exist as Father, the Son and the Holy Spirit. I believe the best book to explain Trinity is the book of John chapters 12 to 17. These chapters I believe describe the unity and distinction of the Father, the Son and the Holy Spirit.
Some visual aid may be needed because how can three be one ? I suggest you try this. Out of a cardboard or paper make two equal circles using compass. Make one circle as is but divide the other circle into three equal parts using protractor. The two circles are still the same but one circle has three equal parts. The second circle is not three circles but three parts forming one circle.
One more suggestion on the three parts of one circle, place the verse numbers on those referring to the Fatheron one part, verse numbers for the Son on one part, and verse numbers for the Holy Spirit on the third part.If the verse numbers are too many make bigger circles. I used one 8 and one half inch by 11 inches paper or board to make one circle.Then divide the circle into three equal parts.