Here the word "heart" is a metonym for the mind and thoughts. This represents the person who thinks. Alternate translation: "The person who does right ponders what to say before he answers" (See: [[rc://en/ta/man/jit/figs-metonymy]] and [[rc://en/ta/man/jit/figs-synecdoche]])
The writer speaks of wicked people's mouths as if they were containers and speaks of evil as if it were the liquid that filled them. When wicked people speak, their mouths pour out the liquid. The word "mouths" represents those who speak. Alternate translation: "wicked people are always saying evil things" (See: [[rc://en/ta/man/jit/figs-metaphor]] and [[rc://en/ta/man/jit/figs-synecdoche]])
It may be more natural in you language to translate all these words as either singular or plural. Alternate translation: "the mouth of the wicked person pours out all its evil" or "the mouths of wicked people pour out all their evil"