You might consider responding with appreciation for their summary, adding your own thoughts, or asking a question to encourage further discussion. Here's a suggestion for your response:
"Thank you for sharing that comprehensive overview of CPR principles! I completely agree that understanding the bystander effect is crucial. It's so important to remember that taking initiative can truly make a difference in emergency situations. I was particularly interested in how you mentioned different techniques for various age groups. Do you think that having knowledge of these techniques affects a person's willingness to help in an emergency? It seems like being prepared and confident might overcome the hesitation many feel in those moments. What are your thoughts?"
This response acknowledges your classmate's points and prompts further conversation.