How can I send multilingual Thank You pages and Autoresponders?

I'm at a hiccup with the language to email integration part of things now.

How do I set it up so it will send out the thank you page and email in either french or english?

This can be done by setting up multiple THANK YOU PAGES and AUTORESPONDERS then conditionally trigger them based on your needs.

To setup multilingual thank you pages, follow the article linked below.

Complete guide: How-to-Change-Thank-You-Message-Depending-on-the-Language-Used

And to send different emails based on the language, refer to this guide instead.

Complete guide: How-to-Change-Email-Template-Sent-Based-on-the-Language-Used 

Give those a spin and let us know if you'd need more help.