1 - You have implied based on Christian preconceived notions.
2 - What the Scriptures say is that, "There has never been a man upon earth to have done only good and never sinned." Jesus was a man upon earth. Was the writer of Ecclesiastes lying?
3 - Isaiah was from the city of Tecoa in Judah. A Judahite therefore. His people was the People of Judah cut off from the Land of Israel for the sins of my People aka Judah for whom the stroke was due. The stroke of Divine rejection if you read Psalm 78:67-70.
4 - Yet, he aka Israel, bore the sins of many aka Judah, and not of the whole world which Christians claim Jesus did.
5 - The Lord pleased to crush Israel because by crushing Israel, Judah would remain forever as a single People in Jerusalem before the Lord forever. (Psalm 78:67-70)
6 - What does it mean, that we don't need to repent of our sins? And, if we don't need to repent of our sins, Jesus had no need to get sacrifices for our sins.
7 - This is a doctrine from the gospel of Paul. Peter could not write books.
8 - And Gentiles are welcome to join the New Covenant if they want.
9 - And this was written by a Greek man disciple of Paul. Therefore, not Jewish.
1, I am Jewish and Christian both by choice. I have not implied that God is a liar.
2, It was true when it was written of all who had lived up to that point in time.
3, Here is what the verses you refer to say.
Psalm 78
67 He also rejected the tent of Joseph,
And did not choose the tribe of Ephraim,
68 But chose the tribe of Judah,
Mount Zion which He loved.
69 And He built His sanctuary like the heights,
Like the earth which He has founded forever.
70 He also chose David His servant
And took him from the sheepfolds;
4, John 1
29 The next day he saw Jesus coming to him and said, “Behold, the Lamb of God who takes away the sin of the world!
Acts 5
31 “He is the one whom God exalted to His right hand as a Prince and a Savior, to grant repentance to Israel, and forgiveness of sins.
Acts 11
18 When they heard this, they quieted down and glorified God, saying, “Well then, God has granted to the Gentiles also the repentance that leads to life.”
2 Timothy 2
25 with gentleness correcting those who are in opposition, if perhaps God may grant them repentance leading to the knowledge of the truth,
5, This is a Jewish interpretation, but not the only one.
6, Each and every one of us needs to repent of our sins. If you have confessed your sin your sin will be forgiven. See 1 John 1.
7, Peter and Paul are not the only NT authors.
8, This can only be true of the new covenant that has already come to be in Jesus Christ.
9, The NT is entirely Jewish. You can read it for yourself. There is no crime against God in doing so. Any person may need to understand the old testament or the old covenant first.
John 5
39 “You search the Scriptures because you think that in them you have eternal life; it is these that testify about Me;
2 Corinthians 3
15 But to this day whenever Moses is read, a veil lies over their heart;
16 but whenever a person turns to the Lord, the veil is taken away.
Luke 16
29 “But Abraham *said, ‘They have Moses and the Prophets; let them hear them.’
30 “But he said, ‘No, father Abraham, but if someone goes to them from the dead, they will repent!’
31 “But he said to him, ‘If they do not listen to Moses and the Prophets, they will not be persuaded even if someone rises from the dead.’”
Luke 24
27 Then beginning with Moses and with all the prophets, He explained to them the things concerning Himself in all the Scriptures.
John 1
45 Philip found Nathanael and said to him, “We have found Him of whom Moses in the Law and also the Prophets wrote—Jesus of Nazareth, the son of Joseph.”
John 5
45 “ Do not think that I will accuse you before the Father; the one who accuses you is Moses, in whom you have set your hope.
46 “For if you believed Moses, you would believe Me, for he wrote about Me.
47 “But if you do not believe his writings, how will you believe My words?”