God is absolutely holy and pure, and there's only one thing God can't do: He can't do anything that is against His nature. In other words, the one thing God can't do is sin.
Why, then, doesn't God do something about all the evil in the world? I've asked myself that question hundreds of times -- and to be honest, I don't have a full answer. Some day in heaven, we will understand, but until then, we can only trust in God's goodness, wisdom and sovereignty, even when the world seems dark and in the grip of evil.
It won't always be this way; some day Satan will be defeated and all evil will be destroyed. How do I know this? I know it because by His death and resurrection Jesus Christ conquered all the powers of sin and death and Hell and Satan. And when we put our faith and trust in Him, we know He is with us and will take us to heaven some day. Have you put your life into His hands?
In the meantime, make it your goal to live for Christ and be an instrument in His hands for good. All around you are people who are confused, battered by life, or deceived by Satan's false promises. Ask God to use you to point them to Christ, who alone gives us hope and peace and new life. Jesus' words are true: "I am the light of the world. Whoever follows me will never walk in darkness, but will have the light of life" (John 8:12).