こちらこそ、よろしくお願いします is how I'd respond. Maybe also by following it up with 仲良くしましょうね！

The first part essentially translates to 'Amazing!'. That's 'Ooh, Sugoi'. Then, he said thank you, Arigato gozaimasu. The last part is harder to translate since its use is dependent on context. Yoroshiku, onegaishimasu essentially means "please be kind to me" and infers the reverse to be also provided, but depending on context, it could simply be a kind gesture of gratitude. Check what you said beforehand to gain context. The simplest response would be 'hai'. A better response would be 'kochira koso, yoroshiku onegai shimasu'. note: romaji used above to assist with reading given question level.