Is God willing to prevent evil, but not able? Then he is not omnipotent. Is he able, but not willing? Then he is malevolent. Is he both able and willing? Then whence cometh evil? Is he neither able nor willing? Then why call him God?
Epicurus
God is able to prevent evil. He created a world where we would have free will. Some chose incorrectly and sinned. We're playing out a blip on the radar in the big scheme of things. Soon we'll have no more sin and no more pain and He will get rid of those who chose incorrectly.
2 Peter 3:8
But do not let this one fact escape your notice, beloved, that with the Lord one day is like a thousand years, and a thousand years like one day. 9 The Lord is not slow about His promise, as some count slowness, but is patient toward you, not wishing for any to perish but for all to come to repentance.