Przeczytałam całość raportu w pociągu.

Because przeczytałam is the perfective form, and it tells you the action was completed.

• czytałam = I was reading / I read (without saying whether I finished)
• przeczytałam = I read through / I finished reading

So in this sentence, the speaker is saying she read the whole report, not just part of it.

The ending -łam shows several things at once:

• 1st person singular: I
• past tense
• feminine speaker

So przeczytałam means I read / I finished reading, said by a woman.

If a man says it, it becomes:

• przeczytałem

This is a very important feature of Polish past tense: it agrees with the speaker’s gender.

Because Polish often drops subject pronouns when they are clear from the verb form.

In przeczytałam, the ending already tells us:

• it is I
• it is past
• the speaker is female

So adding ja is usually unnecessary unless you want emphasis:

• Ja przeczytałam całość raportu w pociągu. = I read the whole report on the train.

Without ja, the sentence is more neutral and natural.

Because całość is followed by the genitive case.

So:

• całość = entirety / whole
• raportu = of the report (genitive of raport)

This is similar to English the entirety of the report.

Other similar patterns:

• część książki = part of the book
• koniec filmu = end of the film
• początek dnia = beginning of the day

After nouns like these, Polish often uses the genitive.

Yes. Cały raport is often more natural in everyday speech.

Compare:

• Przeczytałam cały raport. = I read the whole report.
• Przeczytałam całość raportu. = I read the entirety of the report.

Both are correct, but they feel a little different:

• cały raport = simpler, more conversational
• całość raportu = a bit more formal or abstract

So a learner will hear cały raport very often.

Because raport changes to raportu in the genitive singular.

Base form:

• raport = report

Genitive singular:

• raportu = of the report

This happens because of całość, which requires the genitive.

So the structure is:

• całość + genitive
• całość raportu

Because the preposition w takes the locative case when it means in or inside a place.

So:

• pociąg = train
• w pociągu = in/on the train

This is the normal pattern for location:

• w domu = at home / in the house
• w szkole = at school
• w samochodzie = in the car
• w pociągu = on the train

Even though English usually says on the train, Polish uses w, literally in the train.

In natural English translation, it usually means on the train.

Polish uses w pociągu, but English normally says:

• on the train
• on the bus
• on the plane

So do not translate the preposition too literally. In Polish, w pociągu is the standard expression.

The dictionary form is przeczytać.

This is the infinitive, meaning to read through / to finish reading.

Related forms:

• czytać = to read, to be reading, to read habitually
• przeczytać = to read completely

So przeczytałam is the past tense form built from przeczytać.

It describes one finished event.

That comes from:

• the past tense
• the perfective verb przeczytać

So the sentence means the speaker completed the report during a particular train journey, not that she usually reads reports on trains.

If it were about an ongoing or habitual action, Polish would more likely use czytać instead.

Yes. Polish word order is fairly flexible, though different orders change the focus or emphasis.

The given sentence:

• Przeczytałam całość raportu w pociągu.

Other possible orders:

• W pociągu przeczytałam całość raportu.
  Emphasizes where it happened.

• Całość raportu przeczytałam w pociągu.
  Emphasizes the whole report.

The original order is neutral and natural.

Yes, it is correct and natural.

That said, many speakers would probably more often say:

• Przeczytałam cały raport w pociągu.

This sounds a bit simpler and more everyday. But całość raportu is absolutely fine, especially in slightly more formal or careful wording.

A man would say:

• Przeczytałem całość raportu w pociągu.

The only change is:

• przeczytałam → przeczytałem

Everything else stays the same.

A rough guide:

• przeczytałam ≈ pshe-chi-TA-wam
• pociągu ≈ po-CHON-goo

A few useful pronunciation points:

• rz often sounds like the zh in measure
• cz sounds like ch in chop, but harder
• ą is a nasal vowel; before g in pociągu, it sounds close to on / ong
• stress in Polish is usually on the second-to-last syllable

So:

• prze-czy-TA-łam
• po-CIĄ-gu

Because Polish has no articles.

So where English says:

• the whole report
• on the train

Polish simply says:

• całość raportu
• w pociągu

Polish expresses definiteness from context, not with words like a or the.