One thing to remember when translating is that the original Greek didn't use upper and lower case or punctuation, and that (like French and Spanish) nouns have gender, so the word for "it" is the same as the words for "she" and "he". (French has "il" and "elle" for "he" and "she", but no word for "it".)
So the first part of this verse could have been translated as "But the helper, the holy spirit, …".
Most translations are made by people that either believe in, or accept for translation purposes, the doctrine of the Trinity.
So it is natural for them to treat the words as referring to a person and capitalize them.
If the verse instead said:
But the helper, the holy spirit, which the Father will send in my name, will teach you everything, and remind you of all that I have said to you.
there is no reason (other than doctrinal eisegesis) to treat the sentence any differently than:
But the Bible, the Holy Book, which the Father will send in my name, will teach you everything, and remind you of all that I have said to you.
Most Christians would accept that sentence as true, without ever thinking that "Bible" and "Holy Book" are meant to refer to a person.
It's only when one is already aware of the Trinity doctrine that the other interpretation arises.
To those that have no reason to believe that "holy spirit" refers to a specific person, God's holy spirit is literally that: the spiritual power through which God works.
It has no more individual personality than does air or water.
Christians receive some of this spirit at baptism, and combined with their own human spirit it provides them with intimate contact with God.
The Power of the Holy Spirit | United Church of God is an example of this doctrine.