True.
2. The apostles never taught it.
Depends on how the word "trinity" is defined. For instance, if it is simply defined as three persons working together as a unified group, then it is scriptural, but most do not define it that way.
3. The word is not in the scriptures.
This is a poor argument, and one from 'silence', which may or may not be evidence for anything, as there are many words that are "not in the scriptures". For instance the word "Bible" is not in the scriptures.
4. It can't be logically explained.
True.
5. It makes no sense how 1 + 1 + 1 = 1
It depends on how that last "1" is being defined and understood which makes the difference from logical incoherency to logical conherency. For instance if that last "1" is defined as "1" = unified group then it is fine, but if not, then there is a logical incoherency. For instance, it would be true to say 1 + 1 + 1 = 1 (chord, trio), but most do not defined it that way.
Just as an example. Which of the three persons is the Father of the second person?
Is it the 1st person who you call the Father? or is it the Holy Spirit as it says in Matthew 1:18 and Matthew 1:20
This is simple:
The Ancient of Days [Daniel 7:9,13,22 KJB] is
The Heavenly Father which is "Our Father who art in Heaven ..." [Matthew 6:9; Luke 11:2; KJB etc.], even the eternal Father of the Son [John 17:11, etc].
The Son, Jesus Christ is also
a Father [Isaiah 9:6 KJB], see Matthew 2:13-15; Hosea 11:1 [He is true Israel, and as true Israel, he has children, even twelve tribes [James 1:1 KJB], see Revelation 7:3-8; 14:1-5 KJB], then turn to Hebrews 2:9-13; Isaiah 8:8-20 [which Hebrews quotes, see Hebrews 2:13; Isaiah 8:18 KJB], for His disciples are His "children" that the Father gave unto Him [see also John 13:33 KJB], being the true "overcomer" [John 16:33; Revelation 3:21 KJB], the real "Prince" with God [Isaiah 9:6; Daniel 8:11,25, 9:25, 10:13,21, 11:22, 12:1; Acts 3:15, 5:31; Revelation 1:5 KJB], being Lord over His own house, whose house are we [Psalms 98:3; Hebrews 3:6; Jeremiah 31:33 KJB], who himself is the "elect" [Isaiah 42:1; Matthew 12:18; 1 Peter 2:6 KJB] of the Father, in whom all the promises of God find their realization [2 Corinthians 1:20 KJB].
The Holy Ghost/Spirit is also
a Father, for "the man" Christ Jesus was born of the Holy Ghost; see Matthew 1:18; Luke 1:35 KJB, and we as Christians are "babes", even "born again" [1 Peter 1:23 KJB] of the Holy Ghost [John 3:3,5,6,7,8 KJB], and thus we are "born of God", the Holy Ghost [John 1:13; 1 John 3:9, 4:7, 5:1,4,18 KJB]
They are all Fathers, but not the same person/being, nor in the same manner. They are all Creators [Makers; Ecclesiastes 12:1 HOT, see also 'septuaginta'], and thus they are all Head over all creation [body]. This is what is referred to in scripture, as Godhead.