John 6:38

ὅτι καταβέβηκα ἀπὸ τοῦ οὐρανοῦ οὐχ ἵνα ποιήσω τὸ θέλημα τὸ ἐμὸν ἀλλὰ τὸ θέλημα τοῦ πέμψαντός με·

Rough Word-by-word:
because I have come down from the heaven not that I might do the will the mine but the will [of] the him who sent me.

Smooth Translation:
Because I have come down from heaven not that I might do my own will, but the will of him who sent me.

ὅτι conjunction "that, because"

καταβέβηκα verb perfect active indicative 1st singular from καταβαίνω (I come down) "I have come down"

ἀπὸ preposition with genitive "from"

τοῦ definite article genitive singular masculine "the"

οὐρανοῦ noun genitive singular masculine "heaven"

οὐχ adverb of negation "not"

ἵνα conjunction with subjunctive "that"

ποιήσω verb aorist active subjunctive 1st singular from ποιέω (I do) "I might do" (not present active - notice the sigma which I missed at my first glance)

τὸ definite article accusative singular neuter "the"

θέλημα noun accusative singular neuter "will"

τὸ definite article accusative singular neuter "the"

ἐμὸν pronoun accusative singular neuter "my, mine"

ἀλλὰ strong adversative conjunction "but"

τὸ definite article accusative singular neuter "the"

θέλημα noun accusative singular neuter "will"

τοῦ definite article genitive singular masculine "[of] the"

πέμψαντός aorist active participle genitive singular masculine from πέμπω (I send) "him who sent"

με pronoun accusative 1st singular "me"