How should I interpret this and what to respond?

Hello everyone!

Dumb me reminded a friend of mine that we wanted to go out together (something that he forgot…) so after he said he forgot, I said it was not a problem, thinking it was not in his plan and / or he wasn’t interested anymore.

But later he answered something that can be interpreted in two ways “what do we choose to do” OR “we will speak about it later” (for French speakers : “on se dit quoi”)

So dumb me asked if it was a question or an affirmation and he said… it’s an exclamation 😒
I checked later on internet and his sentence actually meant “we will talk about it later” (it comes from his hometown). Dumb me doesn’t want to make another mistake and would like to ask for some advices for a good answer!
Thank you in advance for the answers, I’m lost. 😕