I have no Polish. But if you take a noun, say elephant, then you can say the elephant, an elephant this elephant, ten elephants, because it is a noun. Now make of it a possessive: elephant's
the elephant's, an elephant's this elephant's, ten elephants', These phrases are meaningless, they need a noun which is described by the possessive adjective.
the elephant's trunk, an elephant's trunk, this elephant's trunk, ten elephants' trunks
(noun + 's or s') = possessive adjective/determiner. This is not a noun.
In German we say
Der Mann hat einen Elephanten.
The man has an elephant.
Des Mannes Elephanten ...Here you have what you call a possessive noun, but really it is an adjective
The man's elephant.... 'The man's' or 'Des Mannes' both describe elephant. Does it look like that in Polish?