This cat thinks that it is a duck! Ten kot myśli że to jest kaczka I think, this is a right translate, isn't it?
for that to be correct, it would be something like 'Ten kot myśli, że TO jest kaczką!' afaik
How would you say "This cat thinks that there is a duck"?
And what's the it referring here, the cat or something else?
in Polish sentence "it" is probably the cat, but with some context that could be anything and anyone.
ten kot mysli, że to jest kaczka= This cat thinks that is a duck
ten kot mysli, że jest kaczka= This cat thinks that there is a duck (a duck exists)
ten kot mysli, że jest kaczka= This cat thinks that there (in some place visible on mentioned before) is a duck
It's just to separate the two clauses. It isn't absolutely necessary, but it's the correct way of writing it.
"believes" instead of "thinks" should maybe also work, but i am not a native