We can't know for certain, since no audio recordings exist for obvious reasons, and we'd need a time machine to find a fluent, native speaker we can be confident is using period-correct pronunciations.

We can make educated guesses though, by deconstructing existing descendent languages and tracing back commonalities.

Here's what we've got so far:

https://youtu.be/5NB2Z6pZBNA

Also worthy of note that this sort of writing would've been distinct from daily commoner chit-chat, which would probably be more recognizable to us. Not sure how much of that got recorded and survived through the years though.