Devil or Satan means something like enemy, foe accuser or slanderer. Many may think that an evil being like a devil seems to be a very abstract thought. After all, I, and probably you, haven't seen Satan yet. Like God himself, he is a spiritual being. In our material world - like God too, a spiritual being seems elusive. In addition, the devil probably has an interest in being hidden, after all, the devil is the adversary of God and for sure thinks it is great if someone believes that he doesn't exist, but that God, whom he wants to harm, is responsible for all evil.
Let us imagine that the devil or Satan would not exist - but God who by definition is infinite and almighty. This would mean that all good, love, happiness, perfection, but at the same time all evil, the temptation, hatred, all atrocities of the world come from just one instance, directly from God. This sounds pretty schizophrenic to me.
Now let's imagine that there is the devil / Satan. If God is so almighty, why does he let the devil do what he likes and allow evil? God who is only good certainly does not want anything bad in this world, but God guarantees all people and spirits free will. If God would intervene constantly, we humans would no longer be free. We would be determined by God like robots. Some atheists doubt God precisely because they think he is weak because he allows cruel wars and actions to take place and Christians are persecuted. Jesus - God himself - was persecuted and cruelly killed and God allowed it. The reason? It was the will of the people to do this and God has through this shown us that he respects the free will of the people. It was the free will of the people to lead the first as well as the second world war and God respected it. It is the free will of some people in the world to persecute and exterminate Christians, and the free will of some other people not to better protect these Christians - God allows it and at the same time promises the persecuted an eternal life after death. God respects us humans as we are, he doesn't want robots, he gave and gives us signs that he is there and that he is powerful also if he does not exercise his full power every second. For example Jesus did countless unexplainable miracles, however he always asked those involved if they believe and he did miracles only with their consent. Even virgin Mary was asked if she agrees before God placed himself into her.
As I understand the Bible, there has always been good and bad - the two poles. God did not create evil, he gives everyone the choice and freedom. So everyone has always had the choice of which route to choose. God has always been and only creates good things. God first created the angels, mighty beings of light. They also always had a choice between good and bad. According to the Bible, it was one of those good angels who chose evil - he became arrogant, turned against God, yes, he wanted to be bigger than God himself. The Bible says: “And the great dragon was thrown down, the age-old serpent who is called the devil and Satan, he who continually deceives and seduces the entire inhabited world; he was thrown down to the earth, and his angels were thrown down with him.” (Revelation 12: 9). So Satan comes to earth, takes other angels with him and takes over the power here. This is confirmed in the new testament "We know that we are children of God, and that the whole world is under the control of the evil one." (John 1, 5:19). We are all exposed to the temptations of evil here on earth. The Bible gives Satan as the reason why we humans live here on earth at all and not in paradise - in perfection - as God had intended for us. Satan, in the form of a snake, tried Adam and Eve, they underlie his temptation, and were punished for disobedience - and also because they had chosen not to obey God or to call God and ask what they should believe as the snake told them different things - no, they have treacherously trusted a strange animal more than the being that created them. For this reason they were banished from paradise to this earth where they multiplied and since then spread humanity.
God also creates us humans like angels. Look at babies or toddlers, can they harm a fly? Do they have a spark of malice in them from birth? No, they usually only learn from adults or children that they have passed on and what they have learned from other children. But no matter how we were brought up - in the final stage we always have a choice between good or bad and God has given us a conscience and reason to distinguish one from the other. God gave us the Bible as a guide to a good life and as a warning against evil and the temptation of evil.
At the same time, if there were only good things, wouldn't the world be very one-sided? I would find it very beautiful, but if I didn't know the evil at all, I wouldn't understand how beautiful it really is.
Jesus himself is visited by Satan in the desert during his lifetime on earth after fasting for 40 days. Jesus is tried by him in this weakened state, but he held out to him. We humans are also tempted - but not only by the devil, God also lures us with his promises. We have the choice every day and no matter who we are, whether bishops, students or farmers - we can work on ourselves to always find the right way. Prayer and thus the direct connection with God helps a lot.
If we pray to God for His mercy we may be able to persuade him to intervene positively for us to protect us. In the Bible, God promises us that one day he will intervene - that one day he will clean up and that evil will disappear once and for all. On this day X the wheat will be separated from the chaff. God promises that those who love him and repent their sins will live, those who despise God will perish. We do not know what will happen after this day X - are there still people or are there only eternally enlightened figures of light dedicated to the good? When there is no longer any evil, there is no choice or need for it. I think God is trying to put it off as long as possible to give each individual soul the chance to find him first. But who knows, maybe God will soon be fed up with everything that goes wrong in this world, maybe today or tomorrow - be better prepared for it ...