Sprzedawczyni mówi, żeby nie odcinać metki.

Yes. Sprzedawczyni is a feminine noun meaning saleswoman, female shop assistant, or female clerk.

The masculine form is sprzedawca.

So this sentence specifically tells you that the speaker is talking about a woman working in the shop.

Mówi is the 3rd person singular present tense of mówić, meaning to say or to speak.

So sprzedawczyni mówi means the saleswoman says.

In this kind of sentence, mówi can also feel a bit like tells, especially when it is followed by an instruction:

Sprzedawczyni mówi, żeby...
= The saleswoman says/tells [someone] to...

Here żeby introduces a subordinate clause that expresses what someone wants, says, requests, or recommends.

In English, it often corresponds to things like:

• to
• that
• so that

In this sentence, mówi, żeby nie odcinać metki is roughly the structure of says not to cut off the tag.

So żeby is doing an important grammatical job, even if there is no single perfect one-word English translation.

Because in Polish, subordinate clauses are normally separated by a comma.

Since żeby nie odcinać metki is a subordinate clause depending on mówi, the comma is required:

Sprzedawczyni mówi, żeby nie odcinać metki.

This is standard Polish punctuation.

Polish often uses żeby + infinitive when the person who should do something is understood from context and does not need to be stated explicitly.

So:

Sprzedawczyni mówi, żeby nie odcinać metki
means something like
The saleswoman says not to cut off the tag

The sentence does not explicitly say who should not cut it off, but in context it is probably the customer.

A more explicit version could use a personal verb, for example:

Sprzedawczyni mówi, żebyś nie odcinał metki
if speaking to one man

or

Sprzedawczyni mówi, żebyś nie odcinała metki
if speaking to one woman

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

• odcinać = imperfective
• odciąć = perfective

In instructions, warnings, and prohibitions, Polish very often uses the imperfective to mean do not do this action in a general sense.

So żeby nie odcinać metki sounds natural as an instruction:
not to cut off the tag

Using odciąć here would sound less natural in this context and would focus more on a single completed result.

For a general prohibition, imperfective is the normal choice.

Because after a negated transitive verb, Polish often uses the genitive instead of the accusative.

Here is the pattern:

• affirmative: odcinać metkę
• negative: nie odcinać metki

So:

• metkę = accusative singular
• metki = genitive singular

The basic noun is metka.

This genitive-after-negation pattern is very common in Polish and is one of the things English speakers often have to get used to.

It is genitive singular.

The forms are:

• metka = nominative singular
• metkę = accusative singular
• metki = genitive singular

In this sentence, metki is used because of the negation in nie odcinać.

The sentence does not say this explicitly.

That is normal in Polish. The subject can be left unstated when it is obvious from context.

Here, the understood meaning is probably:

• you should not cut off the tag
• or more generally one should not cut off the tag

So the instruction is aimed at the person buying or handling the item, even though that person is not named in the sentence.

Metka usually means a tag or label, especially on clothing or store items.

In this context, it most likely means the attached shop tag that should stay on the item, for example if the item might be returned or exchanged.

So this is not just any label in the abstract sense; it is probably the physical tag attached to the product.

Not exactly. It is reported speech or an indirect instruction.

The sentence tells you what the saleswoman says.

A direct command would be something like:

Nie odcinaj metki.
= a direct Don’t cut off the tag

or more politely:

Proszę nie odcinać metki.

But in your sentence, the speaker is reporting the saleswoman’s instruction:

Sprzedawczyni mówi, żeby nie odcinać metki.

Yes, depending on the nuance.

For example:

• Sprzedawczyni prosi, żeby nie odcinać metki
  = The saleswoman asks you not to cut off the tag

• Sprzedawczyni każe nie odcinać metki
  = The saleswoman tells/orders you not to cut off the tag

• Sprzedawczyni radzi, żeby nie odcinać metki
  = The saleswoman advises not to cut off the tag

So mówi is fairly neutral. It simply reports what she says, while other verbs can sound more polite, stronger, or more specific.