What exactly to the Old Testament and the New Testament have to do with each other?

In the Old Testament god was a vengeful, angry and a sadist. but in the New Testament god is the opposite. So in short god suffers from bipolar disorder

The Old testament are full of prophecies, events, and it describes the beginning of who, what,why,where,when and how the earth is made. The New testament fulfils some of the prophecies of the Old such as the Messiah Jesus living on earth. The Old Testament are the laws the Jewish people follow ( the Torah), the gentiles ( or the Christians) follow the New Testament they can also follow the Old however. For example. [Genesis 1] " 'The Garden of Eden

1:1 In the beginning God created the heaven and the earth. ' "

The Old Testament is the history of world and the universe, and it defines for us what sin is and how horrible sin is.

The Old Testament also tells us about the Messiah, the Redeemer.

There are over 300 prophesies in the Old Testament which tell us Who the Messiah is.

The first promise of vengence against the serpent who lied to Eve is stated in Genesis 3:15.

The Old Testament does not promote violence in the "an eye for an eye" passage.

The Old Testament limits retribution to "an eye for an eye". Prior to that if you were offended by someone, the usual custom was to kill the other person and often kill his whole family.

The New Testament is the fullfillment of the Old.

Sin is defined in the Old, and in the New the solution to the sin problem is revealed for everyone to see.

God told Abraham about this:

Genesis 18:18

Abraham will surely become a great and powerful nation, and all nations on earth will be blessed through him.

Genesis 22:18

and through your offspring all nations on earth will be blessed, because you have obeyed me."

God repeated this promise to Isaac:

Genesis 26:4

I will make your descendants as numerous as the stars in the sky and will give them all these lands, and through your offspring all nations on earth will be blessed,

The New Testament confirms that I have correctly interpreted the above:

Galatians 3:8

The Scripture foresaw that God would justify the Gentiles by faith, and announced the gospel in advance to Abraham: "All nations will be blessed through you."

King David repeats this message in Psalms 72.

King David was praying that over his son Solomon, but God, the Holy Spirit, puts words into David's mouth which were actually prophetic about Jesus the Messiah.

Jesus quoted from nearly ever book in the Old Testament.

So yes the Old and New Testament are tightly intertwined and the New Testament is the fulfillment of the Old.

Let me explain it like this:

You have a toddler, too young to understand reasoning. Your toddler has this strange obsession with putting his finger in electrical sockets. So, you have to slap his hand every time he gets near the plug so he doesn't get himself killed.

Time passes, and the toddler grows into a teen. You teach your teenager the properties of electricity, why it is used, how it is applied, the differing types of currents, and how electricity makes the world a better place. You don't have to slap his hand anymore, because his concern is more about using the plug to plug in the lamp so he can see, instead of "I wonder what happens when I do this?"

So too, is the difference between the OT and NT. The OT teaches the laws of what is right and wrong.. the slap on the hand for trying to touch the plug. The NT teaches, metaphorically, that the purpose of the plug isn't for your hand to be slapped, it's there so you can plug the light in so you can see... that is, the purpose of all the "Thou Shalts" is for people to see the difference in 'how to love one another' and 'how to hate one another', so we may 'choose loving one another', and not 'choose to hate one another by pretending we love one another'.

The OT, it says in the 10 Commandments "Thou shalt not kill"... the slap on the hand before the purpose can be understood... then, in the NT, Jesus taught "If you even *think* of hating, it's just as bad as killing"... therefore we may 'see' and understand "It's not about the deed of killing, it's about harboring evil thoughts and an evil attitude which is bad, and then acting upon it is just as bad"... plugging in the lamp once we understand the purpose of the plug.

Regarding your examples of 'an eye for an eye' and 'turn the other cheek'... An eye for an eye does not mean vengeance or retribution, it means justice. If my son spills my soda, under OT laws, it is his legal duty to clean it up and get me a new one. Under NT concepts, the concept still applies, that I if spill my son's soda, I should clean it up and get him a new one- but not because I am obligated to, but because I love him so much, and do not want to see him sit in that sticky mess, or be without a cool drink, that I choose to act as such. And for "turn the other cheek", it could be said, then, that when I spilled his drink, and said "I'm sorry, here, let me clean it up and get you a new one", he goes and tells me, "naw, it's no big deal, I'll take care of it".

In the end, it is all about treating one another good, just as you yourself want to be treated good. The OT is the command to do so, the NT explains the why you should do so, even though you are no longer forced to do so.

According to Christian doctrine, man cannot merit salvation through his own repentance. Atonement comes only through the shedding of innocent blood. Throughout the seventh chapter of Jeremiah, however, the prophet proclaims the very opposite message on atonement. Over and over again, Jeremiah loudly declares that God does not want blood sacrifices but rather repentance alone for man's grievous sins.

http://www.outreachjudaism.org/jeremiah31.html

What is G-d's will? The Hebrew Bible says "an eye for an eye", etc. Does G-d want the court to poke out the eye of someone who took out somebody's eye?

G-d revealed that if someone pokes out an eye, the real penalty is that they have to pay monetary compensation for pain, embarrassment, loss of wages, etc. So, if there is really a monetary penalty, why does the Written text say, "an eye for an eye"? The answer is that G-d wanted to inform us that if you do something as terrible as break someone's arm, or blind them, you deserve the same thing to happen to yourself. However, even though in theory you deserve this, it wouldn't really be just or ethical. For example, what if a pianist chops off the hand of an opera singer? The opera singer can still sing, but removing the hand of the pianist would destroy his or her ability to work.

Or what if a person with one eye takes out the eye of someone who has two eyes. That person can still see, but if you remove the one eye of the criminal, he or she will become totally blind. So, while in theory, if you take out someone's eye, that should happen to you, G-d's will for perfect justice would not be served if we carried out such a punishment, and therefore, there is monetary compensation.

In the question about capital punishment, the same applies. The reason that Torah often says that a crime carries the death penalty, is to impress upon us how horrible that crime is. But in truth, G-d is not interested in having people put to death every day. The real message of the Bible is that G-d would rather have people repent and improve their lives (see the book of Ezekiel, chapter 18). In addition, how do we really know that someone committed a crime? Obviously, there have to be witnesses...And G-d established laws of witnesses that were so strict, that it was virtually impossible to ever have a case where someone would get the death penalty. The Talmud says that if the court put one person to death in 70 years, it was a bloody court. In Jewish history, there was almost never a death penalty imposed.

From "Judaism for Everyone" by Rabbi Shmuley Boteach

I have often heard it said that the God of the Old Testament is vengeful, whereas Jesus’ teachings are more humane; that the Old Testament is about law, whereas the New Testament is about love. There are endless comparisons between the Hebrew Bible’s “eye for an eye” law (which has always been interpreted by the Jews to mean financial compensation rather than an eye itself) and Jesus’ magnanimous philosophy of “turn the other cheek.” It is undeniable that Judaism champions law above love, practice above faith, and religious service above theology and dogma, for which it has paid an enormous price in terms of popularity. Judaism maintains wholeheartedly that love without law is nothing more than meaningless sentimentalism, which will ultimately end in cruelty. As the popular saying goes, “He who is kind to those who are cruel will end up being cruel to those who are kind.”

…”Paul’s excoriation and condemnation of the law has directly influenced millions of people to see only oppression in the Torah.” “Judaism rejects these attacks. Law is the ultimate safeguard for love. The separation of law and religion has proved to be a great calamity for human civilization. First, it means that atrocities can be perpetrated in the name of God and no one can say that religious law forbids it. Furthermore, the Christian rejection of law as a religious discipline would guarantee religion’s divorce from the world and its realities. That religion has lost out to secularism as the mainstream guide to human life is a direct result of the detached role that religion began to play when Christianity abrogated the law. To say that religion cannot be about law is to say that religion is not designed to regulate human life!”

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Simple

When Paul invented the blue sky religion known as Christianity he gave non-Jews a way to claim historical validity by allowing them to connect to the NT to the OT and thus to the beginning of Western Civilization

No doubt somewhere in America today some Christian pastor is telling his non Jewish congregation that the Jewish prophets of the OT are also their prophets too.

The Old was to show us how HOLY GOD is and it set up a Theocracy, a church government if you will.

Yet even with a list of do's and don'ts Israel kept turning away from GOD.

GOD promised a new covenant IN THE OLD ONE, where instead of a Theocracy everyone would be accountable for their self and and instead of the laws written on stone and a Priesthood executing judgment on sin, we would have the opportunity to hear GOD'S truth through the gospel have it written on our hearts and be judged by one infallible high priest later,JESUS CHRIST.

The Old Testament was to bring us to CHRIST to show us that on out own we do not have the power to overcome sin.

In the Old Testament you have history, what the Laws of God are, prophecies, a view of what it was like back then, what different Kings went through, their faith in God, some songs and poetry, and some genealogies, and prophecies of the Messiah to come. The word Testament means Covenant. The New Testament gives us direction how to live as Christians, (the word Christian means Christ-like), it tells the genealogy of Jesus (Yeshua), shows where the prophecies of the Old Testament have, are and will be fulfilled, and teaches us who Jesus is.

Are you familiar with any of the 300 or so prophecies in the OT that were fulfilled in Jesus? Let me know. They are very interesting. You might find them exciting to read. I can send some over via email if you like.

Old Testament was before Jesus was around so, less people believed, and things were all chaotic, and people's only means of knowing there was a God was though personal experiences or prophets-if they chose to believe them. So it's almost a picture of where we would be had Jesus not come to show us what to do.

New testament- Jesus arrives- which also causes chaos in a different way, but yea, you can tell that people deffinitely changed for the better after his life, death, and ressurection.

Hope it helps, but idk if it even came close haha.