Why does God ask to kill animals as sacrifices and offerings for sin?

Lamb

The Bible describes in great detail the animal donations on the altar.

A person in the modern world sincerely does not understand why God can be pleased with the killing of innocent animals in order to propitiate God for human sins. This is difficult for a modern person to understand.

As early as the beginning of the Bible, we see that animal sacrifice was a human initiative.

Why do righteous suffer and wicked flourish? Where is justice?

Judge hammer

In this world we often see that people are not treated fairly. We see righteous suffer and wicked flourish. But why is that? According to the Bible, God gives justice to those who are treated unfairly.

The LORD gives righteousness and justice to all who are treated unfairly.

( Psalms 103:6 )

But if God gives justice, then why are we seeing so much injustice around?