Kad počnem kihati u autobusu, odmah tražim maramicu u torbi.

Yes. Kad means when here.

In Croatian, both kad and kada can mean when.

• kad is more common in everyday speech
• kada can sound a bit more formal or emphatic

So Kad počnem kihati u autobusu... means When I start sneezing on the bus...

Počnem means I start or I begin.

Its dictionary form is početi = to begin / to start.

This is a 1st person singular present tense form:

• ja počnem = I start
• ti počneš = you start
• on/ona počne = he/she starts

In this sentence, počnem is used after kad to mean when I start.

Because after početi (to start), Croatian normally uses an infinitive-like complement, not another finite verb.

So:

• počnem kihati = I start sneezing
• not počnem kiham

Here, kihati is the verb to sneeze in its infinitive form.

This is similar to English:

• I start sneezing
• not I start I sneeze

Kihati means to sneeze.

A learner may notice that Croatian often has verb pairs related to aspect:

• kihati = imperfective, ongoing/repeated sneezing
• kihnuti = perfective, to sneeze once / a completed sneeze

In this sentence, počnem kihati means I start sneezing, so the imperfective kihati fits naturally because it refers to the activity beginning, not just one single sneeze.

Compare:

• Počnem kihati. = I start sneezing.
• Kihnem. = I sneeze once.

This is mainly about aspect.

Croatian often uses a perfective verb after kad when talking about the moment something begins or happens:

• Kad počnem... = When I start...

Početi is perfective, so it focuses on the start as a completed point/event.

Počinjati / počinjati-type forms are imperfective and would suggest a more ongoing or habitual process, but for the moment of starting, početi is the natural choice.

So Kad počnem kihati... sounds normal and idiomatic.

Literally, u autobusu means in the bus, but in English we usually say on the bus.

Croatian uses u + locative for being inside an enclosed vehicle or place:

• u autobusu = on the bus
• u vlaku = on the train
• u autu = in the car

So do not translate word-for-word here.
Croatian says u autobusu, while natural English says on the bus.

Because after u when it means in / inside / at, Croatian uses the locative case.

• basic form: autobus
• locative singular: autobusu

So:

• u autobusu = on the bus / in the bus

This is a very common pattern:

• u gradu = in the city
• u stanu = in the apartment
• u autu = in the car

Odmah means immediately, right away, or at once.

In this sentence:

• odmah tražim maramicu = I immediately look for a tissue

It adds the idea that the speaker reacts without delay.

Here tražim means I look for.

The basic verb is tražiti, which can mean:

• to look for / search for
• sometimes to ask for / request, depending on context

In this sentence, because of maramicu u torbi (a tissue in my bag), the meaning is clearly:

• I look for a tissue in my bag

So the speaker is searching for it, not asking someone else to give it to them.

Because maramicu is in the accusative case.

The verb tražiti takes a direct object, and direct objects are often in the accusative:

• basic form: maramica = tissue / handkerchief
• accusative singular: maramicu

So:

• tražim maramicu = I’m looking for a tissue

This is a very common feminine noun pattern:

• knjiga → knjigu
• torba → torbu
• maramica → maramicu

Maramica can mean either tissue or handkerchief, depending on context.

In modern everyday situations, especially with sneezing, many learners will understand it as tissue. But it can also refer to a cloth handkerchief.

If the context specifically needed paper tissue, Croatian might also use:

• papirnata maramica

But maramica by itself is very normal and natural here.

U torbi is also u + locative.

• basic form: torba = bag
• locative singular: torbi

So:

• u torbi = in the bag

This tells us where the speaker is looking for the tissue.

Compare:

• tražim maramicu u torbi = I’m looking for a tissue in my bag
• stavljam maramicu u torbu = I’m putting the tissue into the bag

That second example uses u torbu (accusative) because it shows movement into the bag, while u torbi (locative) shows location.

Because Croatian distinguishes these by case.

With u:

• u + locative = location (in, inside)
• u + accusative = motion toward/into (into)

So:

• u torbi = in the bag (location)
• u torbu = into the bag (movement)

In your sentence, the speaker is searching inside the bag, so u torbi is correct.

Yes, Croatian word order is fairly flexible, but this version is very natural.

The sentence is structured as:

1. time clause: Kad počnem kihati u autobusu
2. main clause: odmah tražim maramicu u torbi

This is a common pattern:

• When X happens, I do Y.

You could move some elements for emphasis, for example:

• Kad počnem kihati, odmah tražim maramicu u torbi.
• Odmah tražim maramicu u torbi kad počnem kihati u autobusu.

These are possible, but the original sounds smooth and normal.

It most naturally sounds habitual or general:

• Whenever I start sneezing on the bus, I immediately look for a tissue in my bag.

Croatian present tense often expresses repeated or usual actions, especially in sentences with kad:

• Kad dođem kući, pijem kavu. = When I get home, I drink coffee.

So your sentence suggests a typical reaction, not necessarily one single event.

Yes, and it would slightly change the nuance.

• Kad počnem kihati... = When I start sneezing...
• Čim počnem kihati... = As soon as I start sneezing...

Čim emphasizes immediacy more strongly. Since the main clause already has odmah (immediately), čim would make the timing even more explicit.

For example:

• Čim počnem kihati u autobusu, odmah tražim maramicu u torbi.

This is grammatical, though with both čim and odmah, the sentence becomes quite strongly focused on quick reaction.

No. Croatian usually omits subject pronouns when they are clear from the verb form.

• počnem already tells us the subject is I
• tražim also tells us the subject is I

So:

• Kad počnem kihati u autobusu, odmah tražim maramicu u torbi. = natural
• Kad ja počnem kihati u autobusu, ja odmah tražim maramicu u torbi. = possible, but usually unnecessary unless you want emphasis or contrast

Croatian is a pro-drop language, so leaving out ja is normal.

Because the sentence begins with a subordinate clause:

• Kad počnem kihati u autobusu = dependent clause
• odmah tražim maramicu u torbi = main clause

When the subordinate clause comes first, Croatian normally separates it with a comma.

So the comma works much like in English:

• When I start sneezing on the bus, I immediately look for a tissue in my bag.