Regarding と

I am a little unsure what と indicates in this sentence はい 、この マンション に 住んで いる と 思い ます.

This と means, more or less, ‘that’.
I think that he lives in this block of flats.

It’s not related to と meaning ‘and’, but it’s easy to tell them apart.
と meaning ‘and’ is between two nouns.
と meaning ‘that’ comes after a phrase and is followed by a verb such as ‘say’, ‘think’ or ‘become’.

Very clear explanation thank you.

Wow! I learned more Japanese today with this explanation than with anything else I did.

Thank you!