The Bible has the simplest answer in the debate of evil and suffering. The good news of Christ is the solution to evil. The issue with false solutions is that is places a time limit on God but the Bible tells us that He is currently in the process of defeating evil. The Bible tells us to focus our attention and God and we'll realize there is more to life than the here and now and that a greater reward exists for us in Heaven.
Evil came into existence based on human free will. Adam and Eve chose to eat of the fruit in the Garden of Eden. Evil is the lack of good that should be there and evil exists because of the fall of man. Otherwise mankind would still be perfect. We give into evil when we turn our backs on God and do not follow His commandments.
Christians believe that God allows evil for the purpose of a greater good. In His wisdom He will use suffering for a greater purpose. Because we are limited in knowledge about His ways, we will never understand God's mind. James 1 states that God can allow us to suffer until we reach the end of our rope. But then if we turn to God and He brings us back, then we can use our faith to help others in the same situation. As well, without evil there would be no courage in the world and courage is seen as a positive thing. Also, we could not love our enemies as Jesus taught if there was no evil and no suffering taking place on earth.
In conclusion, the topic of evil and human suffering is one which everyone has an opinion on. Depending on your experiences in life you may have different theories as to why these things happen. But one should realize that no matter why these things happen, Jesus Christ is the solution for all the evil and suffering which takes place in the world. We must believe in him and know that all evil and suffering will come to an end one day.