How can one address the contradiction and atheism resulting from doubt in God's existence and in the Qur'an being the word of God and a miracle, especially when not convinced by the prevailing evidence?

Allah has guaranteed a good life for the believers who perform righteous deeds, and whoever turns away from His remembrance will have a straitened life. The unhappiness resulting from doubt in God's existence is an inevitable consequence of this doubt, for God's existence is a truth that no sane, fair-minded person can deny. Doubt in the Qur'an is caused by weak conviction and insight, for contemplating the Qur'an's miraculous nature is sufficient to be certain that it is the word of God. One must repent to God and return to rectitude before it is too late.