This is the 1830th most frequent Polish word.
bartosz
"Bartosz" is a Polish male given name, equivalent to "Bartholomew" in English.
The word 'Bartosz' functions here as a proper noun, specifically a person's name, serving as the subject of the sentence.
Bartosz mieszka w Warszawie.
Bartosz lives in Warsaw.
In this sentence, 'Bartosz' is used as a proper noun referring directly to a specific person and serves as the subject in a question.
Czy Bartosz może nam pomóc z projektem?
Can Bartosz help us with the project?
Here, 'Bartosza' is the accusative form of the proper noun 'Bartosz', indicating the object of the verb 'znam' (I know).