They use a question to emphasize how amazed they were about their encounter with Jesus. The intense feelings they had while talking to Jesus are spoken of as if they were a fire burning inside them. Alternate translation: "Our hearts were burning ... scriptures." (See: [[rc://en/ta/man/translate/figs-metaphor]] and [[rc://en/ta/man/translate/figs-rquestion]])
The two men were speaking to each other. The word "us" is dual inclusive for languages that make these distinctions. (See: [[rc://en/ta/man/translate/figs-pronouns]] and [[rc://en/ta/man/translate/figs-exclusive]])
Jesus did not open a book or scroll. "opened" refers to their understanding. Alternate translation: "while he explained the scriptures to us" or "while he enabled us to understand the scriptures"