So so means average, not so good and not too bad, just in the middle. For example, how is your day going? So-so. Just like my day is not that fantastic nor too boring. Just as usual.

In North America, "so-so" is an indirect way to say disappointing, slightly bad or bad. Examples: - How is the new restaurant on Main Street? - So-so. I won't go there again. Here is a discussion that mentions the negative connotation that I gave above (in contrast to the neutral denotation that the Collins and Oxford online dictionaries give). https://forum.wordreference.com/threads/so-so-do-we-really-use-it.2581070/

kind of... (kind of good, but not bad)

Informal way of saying somewhat or a little bit. Eg. I am soso friends with that person. I am somewhat friends with that person.