Learn Hardcore Polish: Na rynku kupiono warzywa, a potem ugotowano zupę. - At the market they bought vegetables, and then made soup.

They are the Polish impersonal past forms in -no/-to. They report that an action was performed, but by an unspecified person or people. Think of English generic they or a passive: One bought..., The vegetables were bought..., Someone bought.... Polish uses this to keep the doer unknown or irrelevant. It’s common in narratives, news, instructions, and recipes.

Is this a passive sentence?

Not exactly. It’s an impersonal active-like construction. A true passive would be:

Warzywa zostały kupione na rynku, a potem zupa została ugotowana. In the passive, former objects become subjects in the nominative (warzywa, zupa), and you can add an agent with przez: przez nas, przez kucharza, etc. In the -no/-to construction, the direct object stays in the accusative (see zupę below), and you can’t add an agent.

How would I say it with “we” as the subject?

Mixed or all-male group: Kupiliśmy warzywa na rynku, a potem ugotowaliśmy zupę.
All-female group: Kupiłyśmy warzywa na rynku, a potem ugotowałyśmy zupę. You can add my for emphasis: My kupiliśmy...

Why is it zupę, not zupa? What case are warzywa and zupę?

They’re direct objects, so they take the accusative in affirmative sentences. Zupa (nom.) → zupę (acc.). Warzywa are neuter plural; nominative and accusative look the same: warzywa. Under negation, Polish normally uses the genitive for direct objects: nie kupiono warzyw, nie ugotowano zupy.

Why na rynku and not na rynek? What case does na take here?

With a static location (where?), na takes the locative: na rynku (on/at the market/square). With movement (to where?), it takes the accusative: na rynek (to the market/square).

We are at the square: Jesteśmy na rynku.
We’re going to the square: Idziemy na rynek.

Does rynek mean a marketplace or a town square?

In everyday Polish, rynek usually means the historic main town square. For an actual produce market, you’ll often hear targ, bazar/bazarek, or targowisko. So na rynku often implies “on the (main) square,” though context can make it clear you mean a marketplace.

Why a potem instead of i potem or just potem? Are następnie and później possible?

a potem is very idiomatic for and then, with a slight sense of step/contrast between actions.
i potem is possible but less common in this slot.
potem alone works, especially after a pause: ...; potem ugotowano zupę.
następnie is more formal (next), później is later (not necessarily immediately next).

Do I need the comma before a potem?

Yes. In Polish, a comma is normally used before a when it links two clauses: ..., a potem .... Without a conjunction, use a semicolon or appropriate punctuation: Na rynku kupiono warzywa; potem ugotowano zupę.

Why the perfective verbs (kupiono, ugotowano)? What would the imperfective be?

Perfective marks completed, one-off events—perfect for a sequence of finished actions. Imperfective would be kupowano, gotowano, which suggest ongoing, habitual, or repeated actions:

W soboty na rynku kupowano warzywa, a potem gotowano zupę. (On Saturdays people would buy vegetables and then cook soup.)

Can I specify who did it while keeping kupiono/ugotowano?

No. The -no/-to form is agentless. To name the agent:

Use active: My kupiliśmy..., potem ugotowaliśmy...
Or passive with przez: Warzywa zostały kupione przez... You can, however, add a beneficiary in the dative: Kupiono nam warzywa, ugotowano nam zupę.

How do I say the same thing in the present or future with an impersonal feel?

Use the reflexive impersonal with się:

Present: Kupuje się warzywa na rynku, a potem gotuje się zupę.
Future: Kupi się warzywa na rynku, a potem ugotuje się zupę. Colloquial indefinite 3rd plural also exists: Kupią warzywa, potem ugotują zupę (they), but it implies some generic “they.”

Can I change the word order?

Yes, Polish word order is flexible and used for emphasis:

Warzywa kupiono na rynku, a potem ugotowano zupę. (focus on vegetables)
Na rynku warzywa kupiono, a potem zupę ugotowano. (marked, contrastive focus)
Time adverbs like potem are natural at the start of the clause: Potem ugotowano zupę. Putting potem at the very end (Zupę ugotowano potem) is possible but sounds marked.

How is warzywa understood without articles? Does it mean “some vegetables” or “the vegetables”?

Polish has no articles, so warzywa can mean either, depending on context. If you need to be explicit, use determiners:

jakieś warzywa (some vegetables)
te warzywa (these/the vegetables in question)
tamte warzywa (those vegetables)

How do you pronounce the tricky parts?

Stress is on the penultimate syllable: na RYN-ku, ku-PJO-no, wa-ZHY-wa, a PO-tem, u-go-to-VA-no, ZU-pę.
rz in warzywa sounds like English zh in “vision.”
y in rynek is a close central vowel [ɨ], not like English “ee.”
Final ę in zupę is a nasalized “eh”; at the end of a sentence it often sounds just like “e” with slight nasality.

How would I negate the whole sentence?

Use nie and switch the direct objects to genitive:

Na rynku nie kupiono warzyw, a potem nie ugotowano zupy.

Could I use a different verb than ugotowano?

Yes. Alternatives include:

przygotowano zupę (prepared soup)
zrobiono zupę (made soup; more colloquial/generic) Each carries slightly different nuance; ugotowano emphasizes cooking/boiling.

Where does this -no/-to style typically appear?

News reports and official statements (to de-emphasize the agent)
Instructions and recipes (Dodano sól, Ugotowano zupę)
Notices and summaries (e.g., meeting minutes) It’s neutral and very common in written Polish, and also used in speech.