However reading online this is different from the stuff I had and the code doesn't print out anything when running and testing it. From what I gathered it's supposed to print "I am a duck" but it does nothing at all.

The code you posted here is not supposed to print anything, it makes no animal objects, it invokes no methods on those objects

Duck->new->speak

Animal->new->speak

Your class Duck inherits from Animal
a Duck is a type of animal
Patka je vrsta Životinje
Patka nasljeđuje od Životinja
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