Przy okienku urzędniczka sprawdza oryginał i kopię dokumentu.

Because przy normally takes the locative case when it means by, at, next to.

• basic form: okienko
• locative singular: okienku

So przy okienku means at the window / at the counter window.

Literally, okienko is a diminutive of okno, so it means little window. But in real-life Polish, okienko very often means a service window or counter window, especially in places like:

• offices
• stations
• post offices
• government buildings

So in this sentence, przy okienku is best understood as at the service window / at the counter.

Urzędniczka is a feminine noun meaning female clerk / female office worker / female official.

The masculine form is urzędnik.

So the sentence tells you that the clerk is a woman. Polish often marks gender directly in job titles and nouns referring to people.

Sprawdza is:

• 3rd person singular
• present tense
• from the verb sprawdzać = to check

So it means:

• checks
• or is checking

Polish present tense can often cover both the simple present and the present continuous from English, depending on context.

Because the ending shows present tense.

Compare:

• sprawdza = checks / is checking
• sprawdzała = she was checking / checked
• sprawdzi = she will check or she checks completely in a future sense, from the perfective verb

In this sentence, sprawdza simply gives a present-time action.

Because oryginał is a masculine inanimate noun, and in Polish those often have the same form in nominative and accusative singular.

Here it is the direct object of sprawdza, so it is in the accusative. But the accusative looks identical to the dictionary form:

• nominative: oryginał
• accusative: oryginał

So even though the form does not change, the case still does.

Because kopia is a feminine noun, and feminine nouns ending in -a usually change to -ę in the accusative singular.

• nominative: kopia
• accusative: kopię

Since kopię is also a direct object of sprawdza, it has to be in the accusative.

Because they belong to different noun types.

Both are in the accusative, but Polish nouns form cases differently depending on gender and declension pattern:

• oryginał is masculine inanimate, so accusative looks like nominative
• kopia is feminine, so accusative changes to kopię

So the difference is not about function. They are both objects. The difference is only about noun morphology.

Dokumentu is the genitive singular of dokument.

It is used here because Polish often expresses relationships like:

• original of the document
• copy of the document

So:

• oryginał dokumentu = the original of the document
• kopia dokumentu = the copy of the document

In the full sentence, dokumentu applies to both nouns: oryginał i kopię dokumentu = the original and the copy of the document.

Because the two things are:

• the original
• the copy

of one document.

So there are two physical items, but they both relate to a single document. That is why Polish uses singular dokumentu, not plural.

If there were several documents, you might expect something like dokumentów.

Because Polish, like English, often avoids repetition when one word clearly belongs to both parts of a pair.

So instead of saying:

• oryginał dokumentu i kopię dokumentu

it is more natural to say:

• oryginał i kopię dokumentu

The genitive phrase dokumentu is understood with both oryginał and kopię.

No. Polish word order is fairly flexible because case endings show grammatical roles.

This sentence is natural as:

• Przy okienku urzędniczka sprawdza oryginał i kopię dokumentu.

But other orders are possible, for example:

• Urzędniczka przy okienku sprawdza oryginał i kopię dokumentu.
• Oryginał i kopię dokumentu urzędniczka sprawdza przy okienku.

The meaning stays broadly the same, but the emphasis changes.

Because Polish does not use articles like English the and a/an.

So a noun like urzędniczka can mean:

• the clerk
• a clerk

and dokumentu can mean:

• of the document
• of a document

The exact meaning depends on context. In many real situations, context makes it clear which one is meant.

Yes. That is very common in Polish.

English distinguishes:

• checks
• is checking

But Polish often uses one present-tense form, and context tells you whether the action is habitual or happening right now.

So urzędniczka sprawdza can mean either:

• the clerk checks
• the clerk is checking

depending on the situation.

A few useful points:

• rz in urzędniczka sounds like the Polish ż
• ę in kopię and urzędniczka is a nasal vowel, though in real speech its pronunciation can vary depending on the following sound
• ł in oryginał is pronounced like English w
• ci / ć-type sounds in Polish are softer than ordinary English t or ch sounds

A rough learner-friendly approximation might be:

• przy okienku ≈ pshi o-KYEN-koo
• urzędniczka ≈ oo-zhend-NICH-ka
• sprawdza ≈ SPRAHV-dza
• oryginał ≈ o-rih-GHEE-now
• kopię ≈ KO-pyeh
• dokumentu ≈ do-koo-MEN-too

These are only approximations, but they can help at the start.