Morali smo presjedati u drugom gradu, pa sam na kiosku kupila razglednicu za baku.

Croatian usually drops subject pronouns when they are not needed, because the verb form already shows the person and number.

• morali smo = we had to
• smo tells you it is we
• so mi is usually unnecessary

You can add mi only for emphasis or contrast:

• Mi smo morali presjedati, a oni nisu. = We had to change vehicles, but they didn’t.

Also, in neutral Croatian word order, the auxiliary smo often comes in the second position of the clause, so Morali smo is completely normal.

Morali is the past active participle of morati (to have to / must), used to form the past tense together with the auxiliary smo.

So:

• morali smo = we had to

This participle also agrees with the subject in gender and number:

• morali smo = we had to (masculine plural or mixed group)
• morale smo = we had to (all-female group)

So the sentence suggests that the group included at least one male, or the masculine plural is being used as the default mixed form.

This is about aspect, which is very important in Croatian.

• presjedati = imperfective
• presjesti = perfective

Both relate to changing from one vehicle to another.

In this sentence, presjedati presents the action as part of the journey process:
We had to change vehicles / transfer in another city.

A learner may expect presjesti, and that can also appear in some contexts. But presjedati is very natural when the speaker is focusing on the situation or necessity, not just the completed single transfer.

Very roughly:

• Morali smo presjedati... = We had to be transferring / had to change vehicles
• Morali smo presjesti... = We had to make a transfer / had to change once

In real usage, both can occur depending on nuance, but presjedati here sounds natural.

Even though it looks like it might be related to sjediti (to sit), presjedati here means:

• to change trains/buses/vehicles
• to transfer

So:

• Morali smo presjedati u drugom gradu = We had to change vehicles in another city

It is a common travel verb. For example:

• Moram presjedati u Zagrebu. = I have to change trains/buses in Zagreb.

Because this phrase shows location, not movement.

Croatian uses:

• u + accusative for motion toward something
• u + locative for being in a place

Here, the meaning is:

• in another city

So it must be u drugom gradu:

• drugom = locative singular
• gradu = locative singular of grad

Compare:

• Idem u drugi grad. = I’m going to another city.
  → motion, so accusative
• Bio sam u drugom gradu. = I was in another city.
  → location, so locative

Drugom is the locative singular form of drugi (other / another / second, depending on context).

It agrees with gradu in:

• gender: masculine
• number: singular
• case: locative

So:

• u drugom gradu = in another city

This is adjective agreement. In Croatian, adjectives must match the noun they describe.

Again, Croatian usually omits the subject pronoun when it is clear from the verb.

• sam kupila already tells us the subject is I
• so ja is unnecessary unless you want emphasis

Also, sam is a clitic (a short unstressed word), and Croatian clitics usually go near the second position in the clause.

So:

• pa sam na kiosku kupila... = natural
• pa ja sam... = possible, but marked/emphatic

The sentence sounds neutral and natural without ja.

Yes. Kupila is the feminine singular past participle of kupiti (to buy).

So:

• sam kupila = I bought (said by a woman)
• sam kupio = I bought (said by a man)

This is one of the things English speakers often notice: in Croatian past tense, the verb form shows the speaker’s gender.

So the sentence tells us:

• the speaker in the second clause is female

Na can mean more than just on. In Croatian, many places are used idiomatically with na, and kiosk is one of them.

• na kiosku = at the kiosk / at the newsstand

This is a standard expression. It does not necessarily mean physically on top of the kiosk.

Also, since it refers to location, kiosku is in the locative:

• na kiosku = at the kiosk

Compare:

• Kupila sam novine na kiosku. = I bought newspapers at the kiosk.

Because razglednicu is the accusative singular form, used here for the direct object of kupila.

• nominative: razglednica = postcard
• accusative: razglednicu = postcard (as the thing being bought)

So:

• kupila razglednicu = bought a postcard

This is a normal feminine noun pattern in Croatian.

Because za here means for, and with that meaning it usually takes the accusative.

• baka = nominative
• baku = accusative

So:

• razglednicu za baku = a postcard for grandma

That is why the form is baku.

Pa here means something like:

• so
• and then
• so then

It connects the two actions in a natural narrative sequence:

• we had to transfer in another city,
• so / and then I bought a postcard at the kiosk for grandma

It is not exactly the same as i (and).
Pa often gives a sense of consequence, continuation, or the next step in the story.

Because the sentence is shifting from a group action to an individual action.

• Morali smo presjedati... = we had to transfer
• pa sam... kupila... = I bought...

This is very normal in Croatian. The verb forms alone show the subject:

• smo = we
• sam kupila = I bought (female speaker)

So even without pronouns, the sentence is perfectly clear.

Not very naturally. A word-for-word version would sound awkward in English.

A rough literal breakdown is:

• Morali smo = had-to we
• presjedati = transfer / change vehicles
• u drugom gradu = in another city
• pa = so / and then
• sam = am / have (past auxiliary)
• na kiosku = at the kiosk
• kupila = bought
• razglednicu = postcard
• za baku = for grandma

Natural English would be something like:

• We had to change buses/trains in another city, so I bought a postcard for Grandma at a kiosk.

So it is better to understand the grammar and structure, not translate each word mechanically.