Dworzec był tak zatłoczony, że poczekalnia była pełna ludzi.

Because past-tense forms of być (to be) must agree with the grammatical gender of the subject.

• dworzec is masculine, so we get był
• poczekalnia is feminine, so we get była

So:

• Dworzec był... = The station was...
• Poczekalnia była... = The waiting room was...

This is very different from English, where was stays the same.

Because zatłoczony is an adjective describing dworzec, and adjectives in Polish must agree with the noun in gender, number, and case.

• dworzec is masculine singular
• so the adjective must also be masculine singular: zatłoczony

Compare:

• zatłoczony dworzec = a crowded station
• zatłoczona poczekalnia = a crowded waiting room
• zatłoczone perony = crowded platforms

In the sentence, dworzec był tak zatłoczony literally means the station was so crowded.

It means so ... that ...

So:

• tak zatłoczony, że... = so crowded that...

The whole sentence follows a very common Polish structure:

• Było tak zimno, że nie wyszliśmy. = It was so cold that we didn’t go out.
• Był tak zmęczony, że zasnął. = He was so tired that he fell asleep.

In your sentence:

• Dworzec był tak zatłoczony, że...
• The station was so crowded that...

Here że means that.

It introduces the result clause after tak ... że ...:

• tak zatłoczony, że poczekalnia była pełna ludzi
• so crowded that the waiting room was full of people

This że is extremely common in Polish. It can also appear in many other kinds of sentences, not only after tak.

Because the adjective pełny / pełna / pełne (full) normally takes the genitive case in Polish.

So:

• pełna ludzi = full of people
• not pełna ludzie

This is a very important pattern:

• pełny wody = full of water
• pełna energii = full of energy
• pełne książek = full of books

In your sentence:

• poczekalnia była pełna ludzi
• literally: the waiting room was full of people

That is because ludzie is the nominative plural form, while ludzi is the genitive plural (and also accusative in some contexts).

Here, after pełna, Polish requires the genitive, so you need ludzi.

Compare:

• Ludzie czekali. = The people were waiting.

  • here ludzie is the subject, so nominative

• Poczekalnia była pełna ludzi. = The waiting room was full of people.

  • here ludzi is genitive after pełna

This is a very common irregular noun pattern, so it is worth memorizing:

• nominative plural: ludzie
• genitive plural: ludzi

Not exactly.

Dworzec usually means a station building/terminal, especially a major train station or bus station. It often refers to the whole station area or main building.

Stacja is broader and can mean:

• a station in a more general sense
• a railway stop
• a metro station
• a gas station (stacja benzynowa)
• a TV/radio station (stacja telewizyjna)

So in this sentence, dworzec is a very natural choice because it fits well with poczekalnia (waiting room), which is something you expect in a station building.

Poczekalnia means waiting room.

It comes from the verb czekać (to wait), so it is literally a place for waiting.

Because poczekalnia is feminine, you get:

• ta poczekalnia = this waiting room
• poczekalnia była pełna ludzi = the waiting room was full of people

Yes. That is a very close and natural translation.

A more literal breakdown is:

• Dworzec = station
• był = was
• tak = so
• zatłoczony = crowded
• że = that
• poczekalnia = waiting room
• była = was
• pełna = full
• ludzi = of people

So the sentence is structurally very similar to English.

Yes, Polish word order is more flexible than English, but not every version sounds equally natural.

The original:

• Dworzec był tak zatłoczony, że poczekalnia była pełna ludzi.

is completely natural and neutral.

You could also say:

• Poczekalnia była pełna ludzi, bo dworzec był tak zatłoczony.

But that changes the emphasis slightly and uses bo (because) instead of the so...that... structure.

You might also move words around for emphasis, but the original is the best standard version for a learner.

Yes. In standard Polish spelling, you normally put a comma before że when it introduces a subordinate clause.

So:

• Dworzec był tak zatłoczony, że poczekalnia była pełna ludzi.

That comma is required in normal written Polish.

A rough English-friendly guide:

• Dworzec ≈ DVOR-zets
• był ≈ bihw / bew (the y is not like English ee)
• tak = tahk
• zatłoczony ≈ za-two-CHO-nih
• że = zheh (like the s in measure)
• poczekalnia ≈ po-che-KAL-nya
• pełna ≈ PEW-na
• ludzi ≈ LOO-jee

A few helpful sound notes:

• rz in dworzec sounds like ż
• cz sounds like ch in church, but harder
• ł sounds like English w
• dzi in ludzi sounds like a soft jee

Yes, but it changes the meaning a bit.

• bardzo zatłoczony = very crowded
• tak zatłoczony, że... = so crowded that...

If you use bardzo, you lose the built-in result relationship. The original sentence says not only that the station was crowded, but that it was crowded to such a degree that the waiting room was full of people.

So:

• Dworzec był bardzo zatłoczony. = The station was very crowded.
• Dworzec był tak zatłoczony, że poczekalnia była pełna ludzi. = The station was so crowded that the waiting room was full of people.

They are similar, but not exactly identical.

• pełna ludzi = full of people
• zatłoczona ludźmi = crowded with people

Both can work in many situations, but they emphasize slightly different things:

• pełna ludzi focuses on being filled up
• zatłoczona ludźmi focuses more on crowding

Also notice the grammar difference:

• pełna ludzi → genitive
• zatłoczona ludźmi → instrumental

So Polish often changes case depending on the adjective or expression used.