In our case, we provided about 20 pages of Facebook chats. However, we attached a note saying that the entire conversation on Facebook chat alone exceeds 8600 pages. We wrote that we can provide those 8600 pages if they want. Obviously, they did not ask for them
Just select the "best of" chats and emails, showing you two discussing your relationship, your feelings for each other, and your future. Don't include the daily mundane things talking about what you did that day, what was your dinner like, etc. You could also select a chat for every month, or two weeks, to prove ongoing communication. If you're only sending a few dozen pages, it's probably not too hard for you to translate the most important parts.
A picture is worth a thousand words, so put more work into selecting a variety of photos taken at different times, in different places, and with different people. We also printed about 20 pages of facebook screenshots with posted photos and status updates to show that all our friends knew about our relationship.
We got back all the relationship proofs we sent. The photos and screenshots of Facebook looked rough around the edges, probably they looked at all the pages. They might have shuffled through the receipts and copies of passport stamps. Our chats on whatsapp, skype, skype call logs, emails, facebook chat, seemed untouched. They were in the same clip we sent them in. We also sent 100+ pages of copies of our handwritten letters. I don't think they touched them, either.