Ona potrafi mówić po polsku coraz lepiej.

Yes. In Polish, the subject pronoun is often omitted because the verb ending already shows the person:

• potrafi = he/she/it can / is able to

So Potrafi mówić po polsku coraz lepiej is a perfectly natural sentence.

Including ona adds emphasis, contrast, or clarity, for example if you are comparing her with someone else:

• Ona potrafi mówić po polsku coraz lepiej, ale on jeszcze nie.

So ona is not required, but it is not wrong either.

Potrafi is the 3rd person singular form of potrafić.

It means to be able to, to know how to, or to have the skill to do something.

In this sentence, it suggests ability or skill:

• Ona potrafi mówić po polsku = She can speak Polish / She knows how to speak Polish

It often sounds a bit more like having learned ability than simple possibility.

Compare:

• potrafi = is able to, knows how to
• może = can, may, is allowed/is possible
• umie = knows how to, has learned how to

In many situations, potrafi and umie are quite close.

Because after potrafić, the next verb normally stays in the infinitive.

So the pattern is:

• potrafić + infinitive

Examples:

• Potrafi pływać = She can swim
• Potrafi gotować = She can cook
• Potrafi mówić po polsku = She can speak Polish

Only potrafi changes for person and number here. Mówić stays in its basic dictionary form.

Because Polish commonly uses the pattern:

• mówić po + language

So:

• mówić po polsku = to speak Polish
• mówić po angielsku = to speak English
• mówić po niemiecku = to speak German

This is different from English, where you simply say speak Polish.

Also compare these two ideas:

• zna polski = she knows Polish
• mówi po polsku = she speaks Polish

So po polsku is the normal way to express the language used in speaking.

Because the preposition po requires a specific case here: the locative.

So:

• basic form: polski
• after po: po polsku

This same pattern appears with many language names/adjectival forms:

• po angielsku
• po francusku
• po hiszpańsku

For a learner, it is easiest to remember po polsku as a whole expression meaning in Polish / in the Polish language.

Because lepiej is an adverb, and it describes how she speaks.

The verb here is mówić = to speak, so we need something that modifies a verb:

• dobrze = well
• lepiej = better

Compare:

• Ona mówi dobrze = She speaks well
• Ona mówi lepiej = She speaks better

Forms like lepsza or lepszy are adjectives, and adjectives describe nouns, not verbs.

So:

• lepsza nauczycielka = a better teacher
• mówi lepiej = speaks better

Coraz lepiej is a very common Polish expression meaning:

• better and better
• increasingly better
• better and better over time

The structure is:

• coraz + comparative form

Examples:

• coraz większy = bigger and bigger
• coraz szybciej = faster and faster
• coraz lepiej = better and better

So in this sentence, it shows gradual improvement.

It is natural, but Polish word order is flexible.

This version is neutral and clear:

• Ona potrafi mówić po polsku coraz lepiej.

You could also hear:

• Ona potrafi coraz lepiej mówić po polsku.

That puts coraz lepiej closer to mówić, which some speakers may prefer.

In everyday speech, many people would also simply say:

• Ona mówi po polsku coraz lepiej.

That often sounds a bit more direct and natural if the point is just that her Polish is improving.

So the original sentence is correct, but it is not the only possible phrasing.

The difference is subtle but useful.

• Ona potrafi mówić po polsku coraz lepiej emphasizes ability/skill
• Ona mówi po polsku coraz lepiej simply states that her speaking is improving

In many contexts, the second version sounds more natural if you are talking about progress in language learning.

The first one is still correct, but it can sound slightly more focused on capacity than on the act itself.

Because this sentence describes a general skill, not a single completed action.

• mówić is imperfective and works well for ongoing ability, repeated action, or general speaking
• powiedzieć is perfective and usually means to say / to tell something once, to completion

So:

• potrafi mówić po polsku = she can speak Polish
• potrafi powiedzieć coś po polsku = she can say something in Polish

The second one is much narrower. It is about managing to say a particular thing, not about general speaking ability.

Yes, depending on how you translate it into natural English.

In Polish:

• mówić po polsku

can be translated as:

• to speak Polish
• to speak in Polish

English usually prefers speak Polish, while Polish uses the structure with po.

So the Polish phrase literally points to the language used, while the best English translation is often simpler.