Satan-Evil-Temptation-Freedom-Love-Sacrifice-Eden
Why is there evil in the world if God is loving? Because people have free will, and can choose to be evil.
Why does God allow people to have free will? Because God is loving, and wants to be loved. Love is free, and thus people have the choice to choose between God and not God, aka. Satan.
People are always choosing between God and Satan. Satan represents the temptation to be your own god, to go your own way separate from God. Thus, hell is seen as separation from God.
And so, the question "why does evil exist?" has the same answer as "why doesn't God kill Satan?". Because Satan is that which God is not. Satan is the other option besides God. And we can choose between God and Satan.
Free will means that we have the option to choose between options. Separate from free will is temptation, which is the urge to make a particular decision. We live in a world of free will and temptation, giving room for evil to exist.
Thus we can have free will even without temptations. For we can always choose the options that we are not tempted to do. This solves the issue of "how can we have free will in heaven if there's no sin in heaven?".
This also helps us understand the Garden of Eden. In the Garden, Adam and Eve were created as perfect beings, undying images of God. They walked with God in the Garden, in safety and beauty, without temptations. Except for one, the serpent. The serpent tempted Eve to eat the forbidden fruit. And that tempted Adam to eat it as well. This makes humankind weak to temptation, as even in the Garden with just one source of temptation, we fell for it. And the punishment for that is death, as in, mortality.
So temptation was there from the beginning, despite the fact that God created mankind in his perfect image. And since God is in control of everything, that means that God allows temptation to exist. This could imply that temptation is a tool that allows God to know who loves Him. Since without temptation we would simply choose God without thinking twice. But since love requires self sacrifice, people must sacrifice giving into temptation for God's sake.
For temptation is not just some natural, bodily urge to do something that doesn't quite align with God. It's the God-created force that pulls you away from God, the force that God wants you to resist. Because love can always be demonstrated in some way, and this is the demonstration we as people can give God. To show that we love Him. For you can pretend to love another human being by showering them with material gifts. But theres no material gift you can give God in order to fool him. For God cannot be fooled. Only the conscious opposition to the force that pulls you away from Him, can appease Him in the slightest.
But we always fall short of perfection and we send God mixed signals. Does God know we love him if we constantly give him evidence for the contrary? For God is just, and criminals must be punished. But God is also merciful, and He knows how difficult it is for us to be like Him. And so God died for the crimes of all mankind and payed our ransom. He sacfrificed Himself, for His and our sake. For He is both the punisher, and the one being punished. And He is both the merciful, and the one being shown mercy. For in Him is the purest form of love.
Is there a natural hell and a supernatural hell? Natural hell occurs when you go against nature, or the worldy framework. Supernatural hell occurs when you go against God, the spiritual framework.
In nature, you can't truly escape nature, as you cannot break the laws of nature. You can, however, pervert and corrupt nature by replacing or removing meaning from it. This makes room for example, to hedonism, making pleasure the meaning of all things. So what's supernatural hell then?