And you also , for you have been with me from the beginning.

And -- The Greek word translated as "and" is used as the conjunction "and," but it also is used to add emphasis ("also"). In a series, it can be translated as "not only...but also." After words implying sameness "as."

you  -- The pronoun "you" is used explicitly as the subject of the sentence. When it has no verb, the verb "is" or the previous verb is assumed. When it is already part of the verb, its use here creates emphasis on the "you" as we might say "you yourselves." It is plural.

missing "yourselves"  ---- (MW) The pronoun is used here explicitly as the subject of the sentence. Since this information is already in the verb, the sense is repetitive as we say "you yourselves." "

also -- (WW) The Greek word translated as "also" means "but," "however," and "on the other hand." It joins phrases in an adversarial way. Since it always falls in the second position, translating it as "however" often captures its feeling better.  It can also be an explanation of cause ("so").

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

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."

because -- The word translated as "because" introduces a statement of fact or cause, "for what," "because," "since," and "wherefore."

you -- This is from the second-person, plural form of the verb.

have -- (WT) This helping verb "have" indicates that the verb is the tense indicating an action completed in the past. This is not the tense of the verb here.

been - The verb "been" here is the common form of "to be" in Greek. It means to have a certain characteristic or remain in a certain condition. It also equates terms or assigns characteristics. It is in the present tense.

with  -- "With" is the Greek word that usually means "with" or a related concept such as "among" or "by the means of." With genitive,  it means generally, "with," "together with," "in the midst of," "among," "between." "in common," "along with," "by the aid of," and "in conjunction with."

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

from ---  The word translated as "from" means "from" in both locations and when referring to a source or a cause. It also means the instrument "by" which a thing is done and "away from."

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

beginning. -- "Beginning" is a noun that means "beginning," "origin," "first principles," "first place of power," "empire," and "command." This is the word from which we get both "archbishop," primal bishops who can consecrate other bishops, and "archeology," the study of ancient history.