What is good and evil? why does good exist? why does evil exist? how to understand it correctly? what is it?

We recently answered: We believe that the objective "good" is the eternal ideals and actions as done and suggested by the Perfect God and His Torah. He created a perfect world, which obviously includes challenges enabling us to be independent and have free-will to choose to be good, godly and productive, or the opposite (=bad, evil, wrong, not beneficial in the long-range). In other words part of man's "good" (=his free-will), is the possibility to choose bad, and receive the ramifications. Nevertheless, even if man chooses "bad", in the end, the Perfect God, similar to a wise chess-master, can turn every bad or "wrong" decision into a positive one. In addition, we can always turn around and improve, and this is the natural process of "trial and error" and spiritual evolution.