Urzędniczka mówi, że trzeba podpisać wniosek na każdej stronie.

Yes. Urzędniczka is the feminine form of urzędnik.

• urzędnik = a male clerk / official
• urzędniczka = a female clerk / official

So the sentence tells you that the speaker is referring to a woman. In English, we often just say the clerk or the official, but Polish can make the gender explicit.

Mówi, że means says that.

• mówi = says / is saying
• że = that

So:

• Urzędniczka mówi = The clerk says
• że trzeba... = that it is necessary to...

The comma is normal in Polish before że, because it introduces a subordinate clause. Polish uses commas more regularly than English in this kind of structure.

Trzeba means something like it is necessary, one must, or you have to.

It is an impersonal word. That means Polish does not name the person directly here. The sentence does not say you have to sign with a visible you. Instead, it says more generally:

• trzeba podpisać wniosek = the application needs to be signed / one must sign the application

In context, it usually means you or the person submitting the form must sign it.

Because trzeba is normally followed by an infinitive.

So the pattern is:

• trzeba + infinitive

Examples:

• trzeba czekać = you have to wait
• trzeba zapłacić = you have to pay
• trzeba podpisać = you have to sign

This is a very common Polish structure.

This is about aspect, which is very important in Polish verbs.

• podpisać = perfective
• podpisywać = imperfective

Here, podpisać is used because the sentence is about completing a single action: signing the application. The focus is on the result being finished.

So:

• trzeba podpisać wniosek = the application has to be signed
  meaning the signing must be completed

If you used podpisywać, it would sound more like an ongoing, repeated, or habitual action, which does not fit as well here.

Wniosek is in the accusative case, because it is the direct object of podpisać.

The basic dictionary form is:

• wniosek = application / request / petition

Since wniosek is a masculine inanimate noun, its accusative singular looks the same as its nominative singular:

• nominative: wniosek
• accusative: wniosek

So even though the form does not change, the grammatical role does.

Not always. Wniosek is a formal word and can mean several related things, depending on context:

• application
• request
• motion
• petition

In office or bureaucracy contexts, wniosek often means application form or formal request, which is probably the meaning here.

Here stronie is in the locative singular.

The phrase na każdej stronie means on every page.

Why locative? Because na can take different cases, depending on meaning:

• na + accusative often shows movement onto something
• na + locative often shows location on something

Here we are talking about where the signature must appear: on each page. That is location, so Polish uses the locative:

• strona = page
• na stronie = on the page
• na każdej stronie = on every page

Because każdej has to agree with stronie.

The noun is:

• strona = feminine singular

After na in this meaning, strona becomes locative singular:

• na stronie

So the adjective każda also has to become feminine singular locative:

• każda strona = every page
• na każdej stronie = on every page

So the ending changes because of case agreement.

It can mean both in Polish, depending on context.

• strona = side
• strona = page

In this sentence, because we are talking about signing a wniosek in an office context, na każdej stronie is most naturally understood as on every page.

Yes. Polish word order is more flexible than English, because case endings show grammatical relationships.

This sentence has a very natural neutral order:

• Urzędniczka mówi, że trzeba podpisać wniosek na każdej stronie.

But you could move parts around for emphasis, for example:

• Urzędniczka mówi, że wniosek trzeba podpisać na każdej stronie.
• Urzędniczka mówi, że na każdej stronie trzeba podpisać wniosek.

These are all understandable, but the original version sounds very natural and straightforward.

No. Że is pronounced with the ż sound, not plain z.

• ż sounds roughly like the s in measure or the zh sound in English pronunciation guides
• so że sounds approximately like zhe

This is different from ze, which has a plain z sound.

A more direct version could be:

• Urzędniczka mówi, że musi pan podpisać wniosek na każdej stronie.
  = The clerk says that you must sign the application on every page.
  addressing a man formally

or

• Urzędniczka mówi, że musi pani podpisać wniosek na każdej stronie.
  addressing a woman formally

The version with trzeba is less direct and more impersonal, which is very common in official situations.