But -- (OS) There is nothing in the Greek that can be translated as "but" in the source we use today but it does exist in the source that the KJV translators used.

when -- The Greek word translated as "when" introduces a phrase that explains a certain condition so "whenever" or "since."

the -- The word translated as "the" is the Greek definite article; without a noun, it has the sense of "the one." The Greek article is much closer to our demonstrative pronouns ("this," "that," "these," "those") than the English "the." See this article for more. 

Comforter -- (CW)  "Comforter" is an adjective that means "called to one's aid", "assisting in legal matters", "acting as an advocate", and "summoned." Its acts like a noun when introduced by the definite article. Its sense is "the assistant" but since its root is "invited" perhaps "summoned assistant" is more complete. It has no relationship to "comfort."

is -- (IW) There is nothing in the Greek that can be translated as "is" in the Greek source.

come -- The word translated as "come" primarily means "to start out" but Christ usually uses it to mean "come" but not always. It indicates movement, especially its beginning, without indicating a direction toward or away from anything, so it works either as "start," "come," or "go," but it is more like our phrase "being underway." Our English word "show up" captures both the "start" and "come" ideas. See this article for more.

whom -- The word translated as "whom" is a demonstrative pronoun ("this" "that"), but it often acts as a pronoun "which," "what," "who," "whosoever," "where," "for which reason," and many similar meanings.

I -- The pronoun "I" is used here.  When it has no verb, the verb "is" or the previous verb is assumed. When the subject of the sentence is part of the verb, its explicit use accentuates who is speaking "I." Saying "I myself" captures this feeling in English.

missing "myself" -- (MW)  The subject pronoun repeats the information in the verb so it should be repeated in English like "I myself."

will -- This helping verb "will" indicates that the verb is the future tense. Helping or auxiliary verbs are needed to translate the Greek verb forms into English.

send -- "Send" is from a Greek verb that means "send," "send forth," "send away," "conduct," and "escort." This is the second most common word Jesus uses that is translated as "send out," but this one doesn't have the prefix that has the sense of "out."

unto -- This word "to" comes from the dative case of the following word that requires the addition of a preposition in English. The most common is a "to" for the English indirect object.

you -- The Greek pronoun "you" here is plural and in the form of an indirect object, "to you," "for you," etc.

from -- The Greek preposition translated as "from" has many meanings, many of which depend on the case of its object. With the genitive, the sense is motion, "from the side of," "from beside," and generally "from."

the -- The word translated as "the" is the Greek definite article. When not preceding a noun, takes the meaning of "the one" or, in the plural, "the ones." The Greek article is much closer to our demonstrative pronouns ("this," "that," "these," "those") than the English "the." See this article for more. 

Father, -- "Father" is the Greek noun that means "father" or any male ancestor so "forefathers." It is the word that Christ uses to address his own Father.

even -- (IW) There is nothing in the Greek that can be translated as "even" in the Greek source.

the -- The word translated as "the" is the Greek definite article. When not preceding a noun, takes the meaning of "the one" or, in the plural, "the ones." The Greek article is much closer to our demonstrative pronouns ("this," "that," "these," "those") than the English "the." See this article for more. 

Spirit -- The word translated as "spirit" primarily means "breath," "wind," a "non-material being," and "blast." Like "spirit" in English, it can also mean "attitude" or "motivation.' It also means the "breath of life," from which we get to "spirit" and "spiritual." Its meaning as "the breath of life" is brought out by the idea of creating life. Its meaning as "spiritual" is brought out by the contrast with "physical." Read more about this word in this article on the holy spirit.

of -- This word "of"  comes from the genitive case of the following word that requires the addition of a preposition in English.  The most common is the "of" of possession.

missing "the/this"  -- (MW) The untranslated word is the Greek definite article," the," which usually precedes a noun and, without a noun, takes the meaning of "the one." The Greek article is much closer to our demonstrative pronouns ("this," "that," "these," and "those"). See this article for more.

truth, - The literal meaning of the Greek word for "truth" is "not hidden," and it means what is real as opposed to how things seem. Applied to people, it means "truthfulness" and "sincerity." The opposite of a lie or appearance.

which -- The word translated as "which" is a demonstrative pronoun ("this" "that"), but it often acts as a pronoun "which," "what," "who," "whosoever," "where," "for which reason," and many similar meanings.

proceeds - -  "Proceeds" is a verb that means literally, "to make to go or carry out of" and is translated regularly as "to make to go out of," "to fetch out," and "to march out," but in modern English, we would probably say "exit" here. It is in the form of an adjective used as a noun.

from  -- The Greek preposition translated as "from" has many meanings, many of which depend on the case of its object. With the genitive, the sense is motion, "from the side of," "from beside," and generally "from."

the -- The word translated as "the" is the Greek definite article. When not preceding a noun, takes the meaning of "the one" or, in the plural, "the ones." The Greek article is much closer to our demonstrative pronouns ("this," "that," "these," "those") than the English "the." See this article for more. 

Father, -- "Father" is the Greek noun that means "father" or any male ancestor so "forefathers." It is the word that Christ uses to address his own Father.

he - (CW)- The word translated as "he" is an adjective that highlights its noun as being in a specific place or time from a word that means "there." Used a pronoun, the sense is "that one there" or "this one here." It is not the simple pronoun "he."

shall -- This helping verb "shall" indicates that the verb is the future tense. Helping or auxiliary verbs are needed to translate the Greek verb forms into English.

testify -- "Testify" is the Greek verb that means "to give testimony" and "to bear witness." It has the sense of being true testimony. It is the verb form of the Greek word for "testimony" and "proof," which is the source of our word "martyr."

of  -- (CW) The Greek word translated as "of" means "around" when referring to a place, but in referring to a subject, it means "about," "concerning," "on account of," and "in regard to." This is the way Jesus usually uses it. It is not the word form usually translated as "of."

me: - "Me" is the first-person possessive singular pronoun. This pronoun follows the noun so "of mine."  As a genitive object of a preposition, as here, it means movement away from something or a position away from something else.