Believe in the Gospel and triumphantly defeat the enemy of souls. Our non-belief in the existence of the devil wont save us. The devil exists but there’s nothing to fear as long as God is with us. “If God is with us, who can be against us?”.
1 John 3:8 “Whoever sins belongs to the devil, because the devil has sinned from the beginning. Indeed, the Son of God was revealed to destroy the works of the devil.”