If you do not believe in God, does that mean God doesn't exist? If I don't believe in death, does that change the existence of death?

God is not like you or me. God's name, transliterated into English, is "I AM." He has no beginning or ending. It is not He that needs us, yet He sacrificed His only begotten (brought forth) Son. “For God so loved the world, that he gave his only Son, that whoever believes in him should not perish but have eternal life. For God did not send his Son into the world to condemn the world, but in order that the world might be saved through him." - John 3:16-17