My dear friend....first of all allow me to say that God the creator and sustainer of it all does not allow any of this to happen. we live in a falling world and man kind chose to do his /her own will. This world is covered by sin which came from the fall of Adam and Eve and since then man kind has been covered by sin and will continue to do so until the second coming of our Lord Jesus Christ. He then will make a new heaven and a new earth. You ask why do I believe? well, to say that I and I as in the big pronoun to say ME.... would be to be a bit presumptuos but rather I believe because my Lord found grace and grant me mercy that I may come to the saving knowledge faith of Christ. What He has done for me? many would expect here in this answer to hear: wealth or posessions yet He saved my soul, filled my heart with gladness, my heart with peace and contentment not based on how well things around me go or getting all I want but rather how I respond to those circumstances in His midst. He has giving me a chance to live a life for Him in service and not the other way around....your question says: what has He done for YOU...see that implies selfishness and self worshiping ... me, myself and I . I rather live for Him ...what can I do for His kingdom and His people; how can He use me today, how can I tell others about His goodness and mercy on sinners like all of us. My friend, we all have doubts yet allow me to say this: going to church and having a parent or a family that goes to church does not save you only Jesus Christ does...asking HIm to forgive you of your sins and to save your soul for eternal damnation and to help you change your life and to come into your heart. Believe me He will do what He says He wil do and because He is who He says He is. How do I know? He changed my life from sin living and agony and sadness and pain and loneliness and emptyness and purposelessness and aimlessness to a life of peace in hardship, joy in difficulties, hope in despair, humbleness, service to His kingdom, and the best...I will spend the rest of eternity with Him. Praise be to His name always....amen