Habakkuk wrote a book in the Old Testament part of the Bible. Habakkuk was a prophet (holy man). In his book, Habakkuk complained twice to God. Habakkuk asked God why good people must suffer. And, Habakkuk asks why cruel people seem to succeed.
Firstly, Habakkuk complained that the rulers of his country were wicked. God replied that soldiers from Babylon would attack these wicked rulers (Habakkuk 1:2-11).
But Habakkuk complained to God again. Habakkuk said that God allows cruel people to attack good people (Habakkuk 1:12 to Habakkuk 2:1). God replied that he would punish cruel people. But this does not always happen immediately. But God told Habakkuk to write this down, because God will definitely punish evil people. (Habakkuk 2:2-20).
So, good people must trust God (Habakkuk 2:4). The time will come when God will rule the whole world (Habakkuk 2:14).
The Book of Habakkuk ends with a Psalm (song) - Habakkuk 3. This song says that God will rescue his people.