in orthodoxy, we are taught that the new testament is greater than the old testament, that is why we use the epithet ''old'' for the old testament. it's kind of, the ''new'' testament replacing the ''old''. if there are any contradictions between the two, the new testament prevails. it makes sense. the words of christ are words of god himself, and they prevail the old.
The Old Testament is about how humans lose paradise and have to take a tougher road, trying to find their way via law; knowledge of good and evil.
The New Testament is the story of love and faith where humans have a means to find paradise, again. This implied something similar to Adam and Eve, going back into time, and being given a second chance to not make that same critical choice. This second time they do not to choose law; tree of knowledge of good and evil. Jesus is often called the second Adam and replaces law with the original faith Adam had before the taboo.
The doctrine of the forgiveness of sin is a back door way to do away with law. If you break the speed limit law, and the trooper smiles and forgives you and tells you to slow down and be careful, it is like the law does not apply to you, at that instant of time. Forgiveness of sin neutralizes the power of the law as though the law was not in affect.
God never wanted humans to live under law. In paradise, God specifically created a taboo to push Adam and Eve; humans, away from eating of the tree of knowledge of good and evil, from which law derives. Original sin is connected to humans choosing law, over their original faith in the natural instincts of paradise. The animal does not need a learned system of laws to make moral judgements, but rather they act in a faithful way to their instinctive urges, which integrate them with nature and with each other. Instinct is innate and not learned like law, which is why it requires faith in a hunch.
Jesus did way with law, since law; knowledge of good and evil was never condone by God. The tree of knowledge of good and evil was connected to Satan, not God. The choice of Adam and Eve to ignore God and accept Satan via choosing law, allowed Satan to become the Lord of the Earth, during most of the Old Testament and New Testament up to Revelations. The stop off point is where Satan is thrown from heaven. At that point, Satan's job as Lord of the Earth, was no longer condoned by heaven. This is when Jesus takes over the role as arbitrator for humans between heaven and earth.
Sin derives from law. If you break the law you sin. On the other hand, sin is not imputed when there is no law. Law creates sin, often out of thin air. If we repeal a law, we also repeal the induced sin. How can something assumed to be good, like law, create the evil of sin? Law is not good, but it is both good and evil. All law has a dark side, which often shows up when the self righteous do evil in the name of the law; burn witches.
Law is not always objective but is very often subjective. One can see this in action in all types of countries where the parties in power makes laws for their own convenience and power. In Democratic countries the ruling party while shift the laws to favor themselves and their base. This is not objective and can never lead to objectivity. The result is death and suffering appear with the victims changing each election. Forgiveness of sin places each person above the law, sinless, since sin is not imputed when there is no law.