Breakdown of Wszyscy wiedzą, że zrujnowałeś ten projekt przez swoje lenistwo.
ten
this (m)
wiedzieć
to know
wszyscy
everyone / all (the)
projekt
project
Questions & Answers about Wszyscy wiedzą, że zrujnowałeś ten projekt przez swoje lenistwo.
Why do we use przez here to mean 'because of' instead of z powodu?
While z powodu is neutral, przez followed by the Accusative case is specifically used to express a negative cause or fault. Since laziness ruined the project, przez places the blame on it. If it were a positive cause, you would use dzięki plus the Dative case.
What case is swoje lenistwo in this sentence?
It is in the Accusative case, which is required by the preposition przez. For neuter nouns like lenistwo (and the neuter pronoun swoje), the Accusative form looks exactly the same as the Nominative dictionary form.
Why use swoje instead of twoje for 'your laziness'?
In Polish, when the owner of the object is the same as the subject of the clause, you use the reflexive possessive pronoun swój (here in its neuter form, swoje). The subject of the second clause is 'you' (zrujnowałeś), and it is your laziness, so swoje is required.
Why does ten projekt look like it is in the Nominative case if it is the object being ruined?
It is actually in the Accusative case, acting as the direct object of zrujnowałeś. Because projekt is a masculine inanimate noun, its Accusative form is identical to its Nominative form.