Jesus, our High Priest

The author of the Hebrews expounds his theory of the High Priesthood of Jesus in chapter 5. First of all, he defined a high priest as someone
1) chosen from among men
2) appointed by God (explained later in Hebrews 5:4)
3) who acts on behalf of men in relation to God
4) to offer gifts and sacrifices for sins (Hebrews 5:1)
First of all, Jesus must be truly a man. The humanity of Jesus has never been an issue throughout the history of Christian theology. Even his divinity is NOT an issue. Rather, how the two manage to come together without destroying his humanity has generated a lot of controversies and heresies.
Since a high priest is chosen from among the people, he should be sympathetic with the weaknesses of his brethren> It is because he himself is also beset with weakness.
He can deal gently with the ignorant and wayward, since he himself is beset with weakness (Hebrews 5:2).
Notice that this does not apply to Jesus because Jesus has no sins.
For we have not a high priest who is unable to sympathize with our weaknesses, but one who in every respect has been tempted as we are, yet without sin (Hebrews 4:15).
Yet, his superiority over us does not induce him to pride and arrogance. Instead, Jesus is meek and merciful towards sinners.
According to the author of the epistle to the Philippians, Jesus did not grasp / insist on his equality with God to appoint himself a High Priest. He humbled and emptied himself to become man (Philippians 2:6-7).
Similarly, the author of Hebrews explains that Jesus did not exalt himself.
So also Christ did not exalt himself to be made a high priest, but was appointed by him (Hebrews 5:5)
From among men, Jesus was appointed by God to become a High Priest.
Unlike kings who act on behalf of God and prophets who speak on behalf of God, the major function of a High Priest is to act on behalf of men in relation to God. Jesus accomplished these three roles perfectly in his earthly ministry. We Christians partake in these three roles of his when we are baptized.
How did Jesus perform his priestly role on earth? According to the author of Hebrews,
In the days of his flesh, Jesus offered up prayers and supplications, with loud cries and tears, to him who was able to save him from death, and he was heard for his godly fear (Hebrews 5:7).
Representing all mankind, Jesus prayed with loud cries and tears, tears for those too stubborn to shed a drop of tear. In the end, Jesus himself became the sacrifice to be offered up, to take away the sins of the world.
So far so good, but the author of Hebrews made things complicated with the following statement.
Although he was a Son, he learned obedience through what he suffered (Hebrews 5:8).
Why did Jesus need to learn, in particular, to learn obedience? Is it because of his human nature? Is it a necessary procedure to raise the human nature to a higher level? The author left it unexplained.
and being made perfect he became the source of eternal salvation to all who obey him (Hebrews 5:9).
The Son of God was made perfect through his sufferings. The author of Hebrews previously gave another explanation: as a pioneer of our salvation, as our life model, Jesus must suffer (Hebrews 2:10). Now, the author develops this suffer theme: Jesus must suffer to become the source of eternal salvation for us (Hebrews 5:9). Now we know two reasons why Jesus must suffer.

Dear Lord, Most Excellent High Priest, I pray for our Pope and Cardinals. Protect them from evil assaults. Through them, may Your grace be channelled. Amen.

Appendix:
Thou art my Son, today I have begotten theeυἱός μου εἶ σύ, ἐγὼ σήμερον γεγέννηκά σε· (Hebrews 5:5b, Psalm 2:7b)

Thou art a priest for ever, after the order of Melchizedek.
σὺ ἱερεὺς εἰς τὸν αἰῶνα κατὰ τὴν τάξιν Μελχισέδεκ, (Hebrews 5:6b)
Σὺ εἶ ἱερεὺς εἰς τὸν αἰῶνα κατὰ τὴν τάξιν Μελχισεδεκ. (Psalm 109:4b LXX, Psalm 110:4b MT)