Learn Hardcore Croatian: Još uvijek čekamo autobus na stanici. - We are still waiting for the bus at the station.

Još čekamo autobus.
= We are still waiting for the bus.
Još uvijek čekamo autobus.
= We are still waiting for the bus. (often a bit more expressive or emphatic)

Još uvijek often sounds a little stronger, as if you are stressing that the situation is taking longer than expected, or you are commenting on it more emotionally. Još alone is more neutral and slightly shorter/colloquial.

So yes, Još čekamo autobus is perfectly fine and commonly used.

Where do još and još uvijek usually go in the sentence? Can I move them around?

In neutral word order, they usually come early in the sentence, before the verb:

Još čekamo autobus.
Još uvijek čekamo autobus.

Other possible positions:

Autobus još čekamo na stanici. (Sounds marked/emphatic, stressing još.)
Na stanici još čekamo autobus. (Stresses the place first, then the fact that you are still waiting.)

The most natural and common version is exactly what you have:

Još uvijek čekamo autobus na stanici.

Moving još (uvijek) later in the sentence is possible but usually sounds either poetic, very emphatic, or slightly unusual in everyday speech.

Why is there no word for are in čekamo? How does Croatian express we are waiting?

Croatian does not have a separate continuous tense like English (we are waiting).

The simple present tense covers both:

Čekamo autobus.
= We wait for the bus.
= We are waiting for the bus.

The verb čekati is conjugated in the present:

ja čekam – I wait / I am waiting
ti čekaš – you wait / you are waiting
on/ona/ono čeka – he/she/it waits / is waiting
mi čekamo – we wait / we are waiting
vi čekate – you (pl/formal) wait / are waiting
oni/one/ona čekaju – they wait / are waiting

So English we are waiting is simply čekamo in Croatian.

Why is mi (we) not in the sentence? How do I know it means we?

Croatian is a pro‑drop (null-subject) language: if the subject is clear from the verb ending, you usually leave the pronoun out.

Čekamo autobus.
The ending ‑mo tells you it is we, so mi is not necessary.

You can say:

Mi još uvijek čekamo autobus na stanici.

but this usually adds emphasis, like:

We are still waiting for the bus at the station (as opposed to someone else, or contrary to what someone thinks).

In neutral, everyday speech, just čekamo is enough to mean we are waiting.

Why is it čekamo autobus and not čekamo za autobus like in English wait for the bus?

In Croatian, the verb čekati already includes the idea to wait for, so you normally do not add a preposition:

čekati nekoga/nešto – to wait for someone/something

Examples:

Čekam prijatelja. – I am waiting for a friend.
Čekamo autobus. – We are waiting for the bus.

Using čekati za in this sense is non‑standard or influenced by English and should be avoided in correct Croatian.

Why is it autobus and not some changed form? What case is autobus here?

Autobus is in the accusative singular, used for the direct object of the verb.

For masculine nouns ending in a consonant, the nominative and accusative singular have the same form when the noun is inanimate:

Nominative: autobus – subject
- Autobus kasni. – The bus is late.
Accusative: autobus – object
- Čekamo autobus. – We are waiting for the bus.

So the form does not change here, but its function does: in this sentence, autobus is the object of čekamo, so it is in the accusative.

What does stanica exactly mean? Is it a bus stop, a station, or something else?

Stanica is a general word meaning stop or station, depending on context.

Common combinations:

autobusna stanica – bus stop (can be a simple stop or a small station)
tramvajska stanica – tram stop
željeznička stanica – railway station (also željeznički kolodvor)

In many everyday contexts, stanica alone, when talking about autobus, will be understood as bus stop or bus station, depending on the local norm and context.

So na stanici can usually be taken as at the bus stop / at the station, and context clarifies which is more accurate.

What case is na stanici, and why does stanica change to stanici?

Na stanici is locative singular of stanica with the preposition na.

For feminine nouns ending in ‑a, the locative singular usually ends in ‑i:

Nominative: stanica – station/stop (subject)
Locative: (na) stanici – at the station/stop

The preposition na + locative = location (where?):

Na stanici čekamo autobus. – We are waiting for the bus at the station/stop.

Compare:

na stolu – on the table
u kući – in the house

So na stanici literally means on/at the station/stop, and the ‑i ending signals the locative.

What is the difference between na stanici and na stanicu?

Both use the preposition na, but with different cases and meanings:

na stanici – locative; answers where?
- Još uvijek čekamo autobus na stanici.
  We are still at the station/stop waiting for the bus.
na stanicu – accusative; usually answers where to? (destination)
- Idemo na stanicu.
  We are going to the station/stop.

So:

Gdje smo? (Where are we?) – Na stanici.
Kamo idemo? (Where are we going to?) – Na stanicu.

Could I say Još uvijek smo na stanici i čekamo autobus? Is that different from the original sentence?

Yes, that is correct, and it is slightly more explicit:

Još uvijek čekamo autobus na stanici.
Focus: you are still waiting; na stanici just specifies where.
Još uvijek smo na stanici i čekamo autobus.
Focus: you are still at the station, and (in addition) you are waiting for the bus.

The second version more clearly separates location (smo na stanici) and action (čekamo autobus). It can feel a bit more detailed or explanatory. In everyday speech, the original shorter sentence is more typical.

Is the word order fixed? Could I say Na stanici još uvijek čekamo autobus?

Croatian word order is relatively flexible, and your alternative is correct:

Na stanici još uvijek čekamo autobus.

This version:

puts emphasis on the place first (Na stanici),
then adds the information that you are still waiting.

All of these are grammatically fine, with slightly different emphasis:

Još uvijek čekamo autobus na stanici. (neutral; focus on still waiting)
Na stanici još uvijek čekamo autobus. (focus on where you are)
Autobus još uvijek čekamo na stanici. (strong focus on autobus and the fact that the waiting continues)

Neutral, most natural everyday choice is usually the original sentence.

How would I say We were still waiting for the bus at the station in Croatian?

You typically use the imperfective čekati with a past auxiliary:

Još uvijek smo čekali autobus na stanici.

Breakdown:

još uvijek – still
smo – we were (auxiliary verb for past tense)
čekali – waited / were waiting (past active participle, masculine plural)
autobus – the bus (accusative)
na stanici – at the station/stop (locative)

If the group is all-female, you would use čekale instead of čekali:

Još uvijek smo čekale autobus na stanici.

How do I conjugate čekati in the present tense for all persons?

Present tense of čekati (to wait):

ja čekam – I wait / I am waiting
ti čekaš – you wait / you are waiting
on/ona/ono čeka – he/she/it waits / is waiting
mi čekamo – we wait / we are waiting
vi čekate – you (pl/formal) wait / are waiting
oni čekaju – they (masc.) wait / are waiting
one čekaju – they (fem.) wait / are waiting
ona čekaju – they (neuter plural) wait / are waiting

Your sentence uses čekamo = we are waiting.