"A fool does not care about understanding, but only about" This means the fool considers "understanding" the opposite of pleasure. Alternate translation: "A fool detests understanding and only finds pleasure in" (See: [[rc://en/ta/man/translate/figs-litotes]])
This means that the fool only finds pleasure in telling other people what he feels and desires in his heart. Alternate translation: "but only in telling others what is in his own heart" (See: [[rc://en/ta/man/translate/figs-explicit]])
The contents of a person's heart refers to the person's thoughts and feelings. Alternate translation: "what he thinks" (See: [[rc://en/ta/man/translate/figs-metonymy]])