I believe Jesus is the son of God, who died on the cross so that all who believe in him, shall not perish but have ever-lasting life.
It is a matter of faith. I have never doubted the existence of God the Creator, Jesus the Savior and the Holy Spirit which is always with us.
Bad things happen because when we were created we were given free will and some people chose to do bad things.
Can I explain every calamity, disaster or other unpleasant event that has ever happened--no. However, I believe I will understand when I meet my Lord.