One way, click the quote button in the message you want to respond.
2.Then edit the quote and type your response.
3. Then, copy everything.
4. Click the back button on your browser.
5. Go to the next message you want to quote and click the quote button.
6. Place your cursor in the front of the message. Click paste or (ctrl + v).
7. Go to the end of the message. Type your response.
8. Repeat as needed.
Hope this helps. Someone else may have a better method.