Moja córka urodziła się wtedy, kiedy mieszkaliśmy jeszcze w tym mieście.

Because in Polish, urodzić się is the normal verb for to be born.

• urodzić by itself usually means to give birth to
• urodzić się means to be born

So:

• Matka urodziła córkę = The mother gave birth to a daughter
• Córka urodziła się = The daughter was born

The się is not optional here. It is part of the verb expression.

Because the subject is moja córka (my daughter), and córka is feminine.

In the Polish past tense, the verb agrees with the subject in gender and number:

• urodził się = masculine singular
• urodziła się = feminine singular
• urodziło się = neuter singular

Since córka is feminine, the correct form is urodziła się.

Because moja córka is the subject of the sentence, so it is in the nominative case.

• moja córka = nominative, used for the subject
• moją córkę = accusative, used for a direct object

Here, the daughter is the one who was born, so she is the subject.

Yes, kiedy alone could work:

• Moja córka urodziła się, kiedy mieszkaliśmy jeszcze w tym mieście.

But wtedy, kiedy adds emphasis and makes the timing more explicit. It is similar to at the time when in English.

So:

• kiedy = when
• wtedy, kiedy = at the time when / when exactly

It is a natural structure in Polish, especially when the speaker wants to highlight the time relationship clearly.

Here jeszcze means still.

So mieszkaliśmy jeszcze w tym mieście means:

• we were still living in that city

It suggests that later, the speakers stopped living there.

Common meanings of jeszcze include:

• still
• yet
• more / another

In this sentence, still is the correct idea.

Mieszkaliśmy is the past tense form of mieszkać (to live / reside) for we.

Breakdown:

• mieszka- = verb stem
• -li- = past tense plural marker
• -śmy = we

So mieszkaliśmy = we lived / we were living

A useful detail: in the plural past tense, Polish distinguishes gender:

• mieszkaliśmy = we with at least one male person in the group, or mixed group
• mieszkałyśmy = we if the whole group is female

So this sentence suggests that the speaker is male, or that the we group includes at least one male.

Because Polish past tense verbs often cover both the English simple past and past continuous, depending on context.

So mieszkaliśmy can mean:

• we lived
• we were living

Here, because it describes a background situation at the time the daughter was born, English naturally uses were living, but Polish does not need a separate continuous form.

Because w means in, and when it expresses location, it takes the locative case.

The noun miasto (city) changes in the locative:

• nominative: miasto
• locative: mieście

And ten (this/that, depending on context) also changes:

• nominative neuter singular: to / to miasto
• locative: tym

So:

• w tym mieście = in this/that city

This is a very common pattern:

• w domu = in the house
• w szkole = in the school
• w mieście = in the city

Polish ten / ta / to can correspond to both this and that in English, depending on context.

So w tym mieście could be translated as:

• in this city
• in that city

In your sentence, English may prefer that city because the speaker is referring back to a past situation, but Polish does not need a separate demonstrative the way English often does.

If Polish wants to be more explicitly like that, it can use words such as tamten, but that is not necessary here.

Because kiedy mieszkaliśmy jeszcze w tym mieście is a subordinate clause, and in Polish subordinate clauses are normally separated by a comma.

So the sentence has:

• main clause: Moja córka urodziła się wtedy
• subordinate clause: kiedy mieszkaliśmy jeszcze w tym mieście

Polish uses commas more regularly than English in structures like this, so the comma is required.

Because the sentence combines:

• a completed event: my daughter was born
• an ongoing background situation: we were living in that city

In Polish:

• urodzić się is perfective, because birth is treated as a single completed event
• mieszkać is imperfective, because living somewhere is a duration or ongoing state

This is a very common pattern in Polish:

• perfective verb for the main completed event
• imperfective verb for the background circumstance

Yes. Gdy is often interchangeable with kiedy in this kind of sentence.

So you could say:

• Moja córka urodziła się wtedy, gdy mieszkaliśmy jeszcze w tym mieście.

This is correct and natural.

Very roughly:

• kiedy is very common and neutral
• gdy can sound a bit more literary or formal in some contexts, though it is still common

Both work here.

Yes, Polish word order is fairly flexible, although some versions sound more natural than others.

For example, you could also say:

• Moja córka urodziła się, kiedy jeszcze mieszkaliśmy w tym mieście.
• Wtedy, kiedy mieszkaliśmy jeszcze w tym mieście, moja córka urodziła się.

But the original sentence sounds natural because it presents:

1. the main fact first: My daughter was born
2. then the time clause

Polish often changes word order for emphasis, rhythm, or focus rather than basic grammar.

No, it is not strictly necessary.

You can say:

• Moja córka urodziła się, kiedy mieszkaliśmy jeszcze w tym mieście.

That is perfectly correct.

Adding wtedy makes the timing feel a bit more pointed or deliberate. It is like saying:

• My daughter was born at the time when we were still living in that city

So it is optional, but natural.

Then you would usually change mieszkaliśmy to mieszkałyśmy.

So:

• Moja córka urodziła się wtedy, kiedy mieszkałyśmy jeszcze w tym mieście.

Why?

Because in the past tense plural, Polish distinguishes:

• -liśmy for a group including at least one male
• -łyśmy for an all-female group

This is something English does not do, so it often feels new to English speakers.

No. Urodziła się specifically means was born.

If you want was giving birth, you would use the mother as the subject and a different structure, for example:

• Ona rodziła = She was giving birth
• Ona urodziła dziecko = She gave birth to a child

So:

• córka urodziła się = the daughter was born
• matka urodziła córkę = the mother gave birth to the daughter

That difference is very important.