Testing_ABC_en_tn/rom/01/21.md

became foolish in their thoughts

You can translate this in an active form. Alternate translation: "began to think foolish things" (See: rc://en/ta/man/translate/figs-activepassive)

their senseless hearts were darkened

Here "darkness" is a metaphor that represents the people's lack of understanding. Here "hearts" is a metonym for a person's mind or inner being. Alternate translation: "they became unable to understand what God wanted them to know" (See: rc://en/ta/man/translate/figs-metaphor and rc://en/ta/man/translate/figs-metonymy)