W pociągu czytałam artykuł o zdrowiu, aż dojechałam do pracy.

Because w means in here, and after w when it means location, Polish uses the locative case.

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

A native English speaker may expect on the train, but Polish normally says w pociągu, literally in the train.

Czytałam is the 1st person singular past tense form of czytać (to read) used by a female speaker.

• czytać = to read
• czytałam = I was reading / I read (female)
• czytałem = I was reading / I read (male)

In Polish past tense, the verb agrees with the speaker’s gender in the singular.

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

• czytałam already tells us I and also that the speaker is female
• dojechałam also tells us I and female

So adding ja would usually only be for emphasis:

• Ja czytałam... = I was reading...

Because artykuł is the direct object, so it should be in the accusative case. But for many masculine inanimate nouns, the accusative singular looks exactly like the nominative singular.

• nominative: artykuł
• accusative: artykuł

So the form does change grammatically, but in this case it just looks the same.

Because the preposition o (about) takes the locative case.

• zdrowie = health
• locative singular: zdrowiu
• so: o zdrowiu = about health

This is a very common pattern:

• książka o historii = a book about history
• rozmawiać o pracy = to talk about work

Here aż means something like until, often with a sense of all the way up to that point.

So:

• czytałam artykuł o zdrowiu, aż dojechałam do pracy means
• I was reading an article about health until I got to work

It suggests the reading continued right up to the moment of arrival.

Dojechałam comes from dojechać, which means to get to a place by vehicle / arrive by riding.

So it fits very naturally with a train journey.

It is also perfective, which means it describes a completed event:

• dojechałam do pracy = I arrived at work / I got to work

That contrasts nicely with czytałam, which is imperfective and describes an ongoing action:

• czytałam = I was reading
• dojechałam = I arrived

This combination is very common in Polish: an ongoing background action + a completed event.

Because the preposition do takes the genitive case.

• praca = work
• genitive singular: pracy
• do pracy = to work

Compare:

• do domu = home
• do szkoły = to school
• do miasta = to the city

Yes. Here do pracy means to work in the sense of to the workplace / to one’s job location.

Polish often uses praca this way:

• Idę do pracy = I’m going to work
• Dojechałam do pracy = I got to work

It does not mean in order to work here.

Czytałam is used because the action is presented as ongoing during the train ride.

• czytałam = I was reading / I read
• przeczytałam = I read through / I finished reading

If you said przeczytałam artykuł, it would usually mean you finished the article. But this sentence focuses on the activity in progress up to the point of arrival, so czytałam is the natural choice.

Because aż here introduces another clause:

• aż dojechałam do pracy

In Polish, clauses like this are normally separated by a comma.

So the comma marks the boundary between:

• W pociągu czytałam artykuł o zdrowiu and
• aż dojechałam do pracy

Yes. Polish word order is fairly flexible, and changing it usually changes emphasis, not the basic meaning.

For example:

• Czytałam artykuł o zdrowiu w pociągu, aż dojechałam do pracy.
• Artykuł o zdrowiu czytałam w pociągu, aż dojechałam do pracy.

The original sentence begins with W pociągu, which puts the setting first: On the train / In the train...

Yes, definitely. In standard Polish, you say:

• w pociągu = on/in the train

Using na pociągu would sound wrong in this meaning. English often uses on for public transport, but Polish usually uses w with pociąg.

Not necessarily. The sentence says the speaker was reading an article until arriving at work, but it does not clearly say whether she finished it.

If you wanted to make completion clear, Polish would more naturally use a perfective verb such as:

• przeczytałam artykuł

As written, the focus is on the ongoing activity, not the result.

Because Polish does not have a separate tense system exactly like the English past continuous. Instead, Polish often expresses this difference through aspect.

• czytałam is imperfective → ongoing/background action
• dojechałam is perfective → completed event

So Polish gets the same effect with aspect, not with a special continuous tense form.