John 5:46

εἰ γὰρ ἐπιστεύετε Μωϋσεῖ, ἐπιστεύετε ἂν ἐμοί· περὶ γὰρ ἐμοῦ ἐκεῖνος ἔγραψεν.

Rough Word-by-word:
if for you were believing Moses, you were believing then me; concerning for me he wrote.

Smooth Translation:
For if you were believing Moses, then you would have believed me, for he wrote concerning me.

εἰ conditional particle "if"

γὰρ post positive conjunction "for"

ἐπιστεύετε verb imperfect active indicative 2nd plural from πιστεύω (I believe) "you were believing"

Μωϋσεῖ proper noun dative singular masculine "Moses"

ἐπιστεύετε verb imperfect active indicative 2nd plural from πιστεύω (I believe) "you were believing"

ἂν correlating particle of condition "then"

ἐμοί pronoun dative 1st singular "me"

περὶ preposition with genitive "about, concerning"

γὰρ post positive conjunction "for"

ἐμοῦ pronoun genitive 1st singular "me"

ἐκεῖνος pronoun nominative singular masculine "he"

ἔγραψεν verb aorist active indicative 3rd singular from γράφω (I write) "he wrote"