“I guess so.”

You are going out to see a movie with a group of several people. Everyone is trying to decide which movie to watch. Someone suggests watching a certain romantic comedy. Several people agree, but someone asks you if you're OK with that choice. You don't really want to see it, but you will go along with what the majority of people want. You answer:

I guess so.

I guess so.

This is an extremely useful phrase. "I guess so" is a phrase for reluctantly agreeing with someone. It's a way of agreeing with something while also showing that you don't completely want to agree.

When you say "I guess so" the stress should fall on the word "guess". The pitch of your voice should also rise on the word "guess" and then fall and rise on "so"