How do you know the athenians god is the god who make the world?
"Now I am going to tell you about this ‘unknown god.’
24 “He is the God who made the world."
https://www.biblegateway.com/passage/?search=Acts+17&version=NIRV
"he" up above can really only refer to "this ‘unknown god’.
two things further:
if you wish to learn more about pronouns and antecedents, I think this is a good website
https://www.quickanddirtytips.com/education/grammar/pronouns-and-antecedents
now this next part I want to say as gently as possible, but we also want to be honest, yes?
the translation quoted above, the NIRV, is intended for people with very basic English reading ability.
if you're having trouble following what it says, is it really realistic to think that you can understand the CCC or the lumen gentium?
if you would like to try a different translation that you think makes it clearer, here's a whole bunch at once!
https://www.biblehub.com/acts/17-23.htm