John 1:30

οὗτός ἐστιν ὑπὲρ οὗ ἐγὼ εἶπον· ὀπίσω μου ἔρχεται ἀνὴρ ὃς ἔμπροσθέν μου γέγονεν, ὅτι πρῶτός μου ἦν.

οὗτός demonstrative pronoun nominative masculine singular "This one/He"

ἐστιν verb present indicative 3rd singular from εἰμί (I am) "he is"

ὑπὲρ preposition with genitive "in front of/before"

οὗ relative pronoun genitive singular "of whom"

ἐγὼ pronoun 1st singular "I"

εἶπον verb aorist active indicative 1st singular from εἶπον (I said) "I said"

ὀπίσω adverb "behind"

μου pronoun genitive 1st singular "me"

ἔρχεται verb present middle deponent indicative 3rd singular from ἔρχομαι (I come) "he is coming"

ἀνὴρ noun nominative masculine singular "the man"

ὃς relative pronoun nominative masculine singular "who"

ἔμπροσθέν preposition with genitive "in front of/before"

μου pronoun genitive 1st singular "me"

γέγονεν verb perfect active indicative 3rd singular from γίνομαι (I come to be) "he came to be"

ὅτι conjunction "because"

πρῶτός adjective nominative masculine singular "before"

μου pronoun genitive 1st singular "me"

ἦν verb imperfect indicative 3rd singular from εἰμί (I am) "he was"

Rough Word-by-word:
This one/He he is on behalf of/for whom I I said after/behind me is coming the man who in front of me came to be because before me he was

Smooth Translation:
This is he for whom I myself said, "After me is coming the man who came to be before me, because before me he was."

Notes:
In this verse John the apostle tells us that Jesus became a man (note his use of ἀνὴρ and γίνομαι, which happens to be in the perfect, I think showing the lasting implications of the incarnation), but he also tells us that Jesus was eternally existing with his use of the imperfect form of εἰμί. What a marvelous way of depicting this great truth that Jesus is both God and man.

Also note the use of positional language. Jesus came after John the Baptist, but preceded him in rank and existence.

It is truly humbling to see the Apostle's ability to express such deep thought grammatically.