Here "heart" represents the people's emotions. Alternate translation: "I will make the hearts of many peoples afraid" or "I will cause many people to be terrified" (See: [[rc://en/ta/man/translate/figs-metonymy]])
The nation of Egypt, symbolized by its king, is spoken of as if it were a building that was collapsing. Alternate translation: "when nations hear about the way I destroyed you" (See: [[rc://en/ta/man/translate/figs-metaphor]])