In John 16:12, it is written,
I still have many things to say to you, but you cannot bear [them] now.
Ἕτι πολλὰ ἔχω λέγειν ὑμῖν ἀλλ᾽ οὐ δύνασθε βαστάζειν ἄρτι (Textus Receptus, 1550)
Does the Bible ever state what these "many things" were?
In John 16:12, it is written,
I still have many things to say to you, but you cannot bear [them] now.
Ἕτι πολλὰ ἔχω λέγειν ὑμῖν ἀλλ᾽ οὐ δύνασθε βαστάζειν ἄρτι (Textus Receptus, 1550)
Does the Bible ever state what these "many things" were?
[Acts 1:2-3 NKJV]
2 until the day in which He was taken up, after He through the Holy Spirit had given commandments to the apostles whom He had chosen,
3 to whom He also presented Himself alive after His suffering by many infallible proofs, being seen by them during forty days and speaking of the things pertaining to the kingdom of God.
According to verse 3, the "many things" were the things pertaining to the kingdom of God. Jesus has been speaking about the kingdom of God during His 3.5 years of earthly ministry as seen in the four gospels. His speaking at the time was limited by time, space and the capacity of His disciples to receive them. However, after resurrection He can intensify His speaking greatly because now He is no longer limited by time and space.
Immediately after resurrection, He trains His disciples for forty days to live by His invisible presence and He continues to speak about the kingdom of God. At the day of Pentecost, He pours His spirit upon them and now they even become the "bearer" of His speaking.
And today He is still speaking to His believers concerning all things of His kingdom through His written word and His anointing deep within (1 John 2:27).
The Ἕτι πολλὰ"(yet many[things]) is implied by 'many words I must say to you, but you cannot hear them now'. The "things" is implied to mean "words", since "things" is not spelled out, yet we know contextually He is speaking, and not some other activity.
What further illustrates this verse is the following,(vs 13-TR)
ὅταν δὲ ἔλθῃ ἐκεῖνος τὸ πνεῦμα τῆς ἀληθείας ὁδηγήσει ὑμᾶς εἰς πάσαν τὴν ἀληθείαν· οὐ γὰρ λαλήσει ἀφ' ἑαυτοῦ ἀλλ' ὅσα ἂν ἀκούσῃ λαλήσει καὶ τὰ ἐρχόμενα ἀναγγελεῖ ὑμῖν
"When however might have come He the Spirit of Truth he will guide you into the truth of all; not indeed will he speak from himself, but whatever he may hear he will speak; and the (things) coming he will declare to you."
Again, the "things" are words, yet Jesus is saying that the Spirit of Truth(Holy Spirit) will speak the words that Jesus would say, in the time they need to hear them.
In conclusion: Ἕτι πολλὰ" defines "Yet many(things)....", the verb "λέγειν"(to say) defines what "things" in English we need to understand.