Why is there suffering and evil?

From the Christian perspective, suffering originates in the broken nature of our world, which stems from humanity's choice to rebel against their creator, Yahweh.
Humans disobeyed the rule that God had given them. This resulted in the what is called "the Fall of Man." Christians who follow the Armenian teachings believe that humans have free will, which is why humans could, and did, disobey God, even though they had been warned that it would lead to suffering and death. Death is a byproduct of the Fall and is the one of the most obvious forms of suffering.
Suffering and evil, according to biblical teaching, exist because humanity chose a world that is apart from God and is therefore deteriorating.
In addition, people make choices that affect other people. When the choices are selfish or ignorant, they often result in suffering.

Further reading: https://www.amazon.com/Problem-Pain-C-S-Lewis/dp/0060652969

Why is there suffering and evil? A more complete statement of this question should include what is implied, and the question restated as “Why is there suffering and evil, if there is an all good God?” or “How can there be an all good God, if there is suffering and evil?”
Christianity answers this question in the following way. Only God is perfect and all good, and His creation, beginning from nothing, has the potential, and is intended to reflect His goodness, but is in a development process toward achieving that. In that process there is clearly a lack of that goodness, which is experienced as evil and suffering, or an imperfect world. In the case of human beings the process for developing the goodness or fullness of God’s life intended for us is done through the great gift of “free will,” which God has given us. It is through the choices we humans make, using that free-will, in confrontations and experiences of evil and suffering, which actually form our identity more and more as sharing in the goodness of God. By loving acts, through exercising our free will, we are actually capable of transforming suffering and evil into the goodness of God within ourselves. This is the message of the Cross of Jesus and His suffering to redeem us from evil, and bring us to the fullness of life. It is the self-sacrifice of pure love. Suffering and love prove not to be incompatible, but rather necessary co-relatives to one another empowering life and goodness through our free choices. The modern day epics of "Star Wars," "Lord of the Rings," and "Harry Potter," with their personal struggles of choosing good over evil teach us this same truth.
If God had created us in a finished state, reflecting His goodness, then we would not have had the opportunity to participate in His creation through our free will. Instead, we would be pre-programmed robots with no free will. If the world was perfect, and there was no evil, we would lack the opportunities to grow in love through our own free choices, and really not ever experience real love at all. For example, there would be no opportunities to serve one another’s needs, because there would be no needs to serve. We would lack the opportunities to escape egocentrism, by having the opportunity to sacrifice for the interests of others. For example, we often hear on the news, how people take great pride in helping each other when natural disasters hit. This demonstrates the human experience and fulfillment of growing in love.
In summary, evil and suffering are the absence of God’s goodness and love, not His creation. At the same time, evil and suffering, can be “redeemed” through the power of human free will, responding in loving acts. The result is the fulfillment of God’s intention for us to fully share in His goodness and life, but as co-creators of that goodness and life through our free will. By our loving acts, we establish our identity as reflecting the goodness of God. It is actually suffering and evil that give us this opportunity.

Suffering, according to Christian tradition, is a way for mortals to test their faith in the divine. In Buddhist traditions, witnessing and experiencing suffering will lead to spiritual enlightenment.
For example, Saint Lawrence of Rome was slowly burned to death on the orders of Roman Emperor Valerian during the persecution of Christians. His suffering, according to Biblical stories, led to ecstasy. Witnesses smelled a fragrant scent rather than the charred remains of human flesh. His martyrdom led to his canonization as a saint.
Evil, as defined by the Abrahamic religions (e.g. Judaism, Christianity, and Islam), is the polar opposite of Good. In Christianity, the dualism of good and evil is mentioned throughout the New Testament. The Bible features various symbolism of good and evil: angels and demons; God and Satan/Lucifer; heaven and hell, et al.
Evil, according to secular Western Philosophy, is more broadly defined, and could be described as negative traits of the human psyche. In Western philosophical schools of thought, humans are capable of both good and evil deeds. Many literary and cinematic works explore the dualism of good and evil within a single character (e.g., the anti-hero).
Why is there suffering?
Suffering is an experience and a human emotion. There is no reason behind it or why it happens. Suffering is an emotional state that almost all humans experience in various levels and forms.
Why is there evil?
Evil, as a concept, is based on what we believe is moral. A person who doesn't abide by society's laws and social moral codes might believe that killing is not evil. The perception of evil is subjective. However, there are universal definitions of evil, such as rape and murder. Evil acts—such as terrorism or mass murder—happen due to various factors: politically-motivated actions; sociopathic and psychopathic behaviors; war; temporary insanity; bouts of anger; and so on.
https://www.biblestudytools.com/dictionary/suffering/