This is the 9701st most frequent Polish word.
zalewskiego
"Zalewskiego" is not a standalone word; it is the genitive form of the surname "Zalewski," meaning "of Zalewski" or "related to Zalewski."
Here, 'Zalewskiego' is used in the genitive case to indicate possession, referring to Zalewski's car.
Widzę samochód Zalewskiego na parkingu.
I see Zalewski's car in the parking lot.
In this sentence, 'Zalewskim' is in instrumental case, reflecting that the speaking interaction happened with Mr. Zalewski.
Rozmawiałem z panem Zalewskim o jego projekcie.
I talked to Mr. Zalewski about his project.
Again, 'Zalewskiego' appears in the genitive case denoting possession.