Learn Hardcore Polish: Ona potrafi prasować koszule, a żelazko szybko robi się gorące. - She can iron shirts, and the iron quickly becomes hot.

potrafić = can/be able to (ability or capability, often implying being capable of doing it successfully).
umieć = know how to (acquired skill; very common in everyday speech).
móc = can/may (permission or possibility). All three are grammatical, but they mean different things:
Ona potrafi prasować koszule = She is capable of ironing shirts.
Ona umie prasować koszule = She knows how to iron shirts (practical skill).
Ona może prasować koszule = She is allowed/able to iron shirts (permission/possibility).

Can I drop the subject pronoun Ona?

Yes. Polish usually omits subject pronouns because the verb ending shows the person. Potrafi prasować koszule is fully natural. Keeping Ona adds emphasis or contrast (she, as opposed to someone else).

Why is the verb in the infinitive (prasować) after potrafi?

Polish verbs of ability/knowledge (like potrafić, umieć, móc) take an infinitive complement. Hence potrafi prasować, not a finite form like prasuje.

Why prasować and not the perfective wyprasować?

prasować (imperfective) refers to the general activity/skill of ironing.
wyprasować (perfective) means to iron something to completion in a particular instance. After ability verbs, Polish typically uses the imperfective for general skill. Potrafi wyprasować koszulę would focus on being able to complete the task successfully this time.

What case is koszule, and why does it look like that?

koszule is accusative plural (direct object of prasować). For non-masculine-personal nouns like koszula:

nominative plural = koszule
accusative plural = koszule (same form)

Why is it plural (koszule) instead of singular (koszulę)?

Polish has no articles, so both are possible:

prasować koszule = iron shirts (in general).
prasować koszulę = iron a shirt (one, or a specific one from context). The sentence talks about a general skill, so plural makes sense.

Why use the conjunction a instead of i or ale?

a signals a mild contrast or a topic switch, often translated as whereas/while.
i is a neutral and.
ale is a stronger but. Here a contrasts her ability with a property of the iron.

Why is there a comma before a?

In Polish, when a connects two independent clauses, a comma is required: …koszule, a żelazko…

Could I move się or szybko around? For example: Żelazko szybko się robi gorące?

Yes. Acceptable variants include:

Żelazko szybko robi się gorące. (as given)
Żelazko szybko się robi gorące.
Żelazko się szybko robi gorące. Polish word order is flexible. Keep się close to the verb and avoid starting a clause with się.

What does robi się mean here?

robić się + adjective means become/get + adjective. So robi się gorące = it gets hot. You can use it with many adjectives: robi się ciemno (it’s getting dark), robi się zimno (it’s getting cold).

Why gorące and not gorący or gorąco?

żelazko is a neuter noun, so the predicate adjective must be neuter singular: gorące.
gorący is masculine.
gorąco is an adverb or a neuter noun meaning heat; jest gorąco = it is hot (generally, e.g., weather).

Could I say Żelazko szybko się nagrzewa instead?

Yes, and it’s very natural. Options with slightly different nuance/register:

Żelazko szybko się nagrzewa. (heats up quickly)
Żelazko szybko się rozgrzewa. (warms up; often about devices or muscles)
Żelazko szybko staje się gorące. (becomes hot; a bit more formal) All are fine.

Why not use instrumental, like gorącym?

Predicate adjectives after verbs like być, stawać się, robić się take the nominative: jest gorące, robi się gorące. Instrumental is used with predicate nouns (e.g., jest lekarzem), not with adjectives.

What’s the difference between robi się gorące and jest gorące?

robi się gorące highlights the process of becoming hot (it gets hot).
jest gorące states the current state (it is hot).

How do I say that she irons shirts with an iron?

Add an instrumental phrase: Ona potrafi prasować koszule żelazkiem. You can also say używając żelazka (using an iron).

Any quick pronunciation tips for tricky parts?

ż in żelazko sounds like the s in measure.
sz in koszule sounds like sh.
się is pronounced roughly like sh-yeh; in fast speech the nasal ę is light.
Stress is on the second-to-last syllable: o-NA po-TRA-fi pra-SO-wać ko-SZU-le, a że-LAZ-ko SZYB-ko RO-bi się go-RĄ-ce.

What’s the difference between żelazko and żelazo?

żelazko = an iron (the household appliance).
żelazo = iron (the chemical element; also iron as a nutrient).