Moja teta će sutra poslužiti juhu, a ja ću donijeti salatu i kruh.

They are forms of the auxiliary verb htjeti used to make the future tense.

In Croatian, one common way to form the future is:

subject + future auxiliary + infinitive

So here:

• Moja teta će poslužiti = My aunt will serve
• ja ću donijeti = I will bring

The forms here are:

• ću = I will
• će = he/she/it will

Because teta is she, the sentence uses će in the first clause. Because ja means I, the second clause uses ću.

Because moja teta is the subject of the clause, so it is in the nominative case.

• moja teta = my aunt as the person doing the action
• moju tetu would be my aunt as a direct object

In this sentence, the aunt is the one who will serve the soup, so nominative is required:

• Moja teta će... = My aunt will...

Because they are direct objects, so they are in the accusative case.

The base forms are:

• juha = soup
• salata = salad

In the accusative singular, many feminine nouns ending in -a change that ending to -u:

• juha → juhu
• salata → salatu

That is why the sentence says:

• poslužiti juhu
• donijeti salatu

Because kruh is a masculine inanimate noun, and in Croatian the accusative singular of masculine inanimate nouns is usually the same as the nominative.

So:

• kruh = bread
• accusative kruh = bread

That is why:

• donijeti kruh = to bring bread

Compare that with masculine animate nouns, which often change in the accusative.

This is because the future auxiliary is a clitic, and clitics usually go in the second position in the clause.

So in the first clause:

• Moja teta = first unit
• će = second-position clitic

In the second clause:

• a ja starts the clause, but a is a conjunction
• ja is the first real element
• so ću comes after ja

That gives:

• Moja teta će...
• a ja ću...

This is very normal Croatian word order.

No, that would not sound right here.

Croatian often does omit subject pronouns, but a clitic like ću cannot usually stand by itself at the beginning of the clause. You would normally say either:

• a ja ću donijeti...
• or rephrase the clause, for example: a donijet ću...

Also, in this sentence ja helps create a clear contrast:

• My aunt will serve the soup, and I will bring the salad and bread.

So ja is very natural here.

A often links two clauses with a slight sense of contrast, switch of topic, or different participant.

Here the sentence shifts from what my aunt will do to what I will do:

• Moja teta će... , a ja ću...

That makes a a very good choice.

If you used i between the clauses, it would sound more like a simple and with less contrast. Croatian often prefers a when comparing or balancing two people’s actions.

Inside the noun phrase, however, i is used normally:

• salatu i kruh = salad and bread

Yes, sutra is quite flexible in position.

Here it appears after the auxiliary:

• Moja teta će sutra poslužiti juhu

That is perfectly natural.

But Croatian word order is relatively flexible, so you could also see things like:

• Moja teta će poslužiti juhu sutra
• Sutra će moja teta poslužiti juhu

The exact placement can slightly change the focus or emphasis, but the meaning stays basically the same.

Because that is how this future-tense structure is formed.

Croatian future 1 is commonly made with:

future auxiliary + infinitive

So:

• će poslužiti
• ću donijeti

The infinitive is the basic dictionary form of the verb, similar to to serve or to bring in English.

These are perfective verbs, which is very natural here because the sentence refers to single completed future actions:

• serving the soup
• bringing the salad and bread

Croatian distinguishes strongly between imperfective and perfective aspect.

Here, perfective verbs fit well because the speaker is talking about specific future events that will happen once:

• poslužiti = to serve, in a completed/event sense
• donijeti = to bring, in a completed/event sense

An English speaker often does not think about aspect much, but in Croatian it matters a lot.

Both are possible, depending on context.

• moja teta = my aunt
• teta = aunt / the aunt, depending on context

In this sentence, moja makes it explicit whose aunt is meant. Without moja, the sentence could still be grammatical, but it would be less specific unless the context already made it obvious.

Sutra is an adverb meaning tomorrow, so it is not functioning like a noun here and you do not usually analyze it as taking a case in this sentence.

It simply tells you when the action will happen:

• će sutra poslužiti = will serve tomorrow

So a learner should think of sutra here as a time adverb.

Yes. Croatian allows another common future pattern where the infinitive loses its final -i and the clitic attaches after it:

• donijet ću
• poslužit će

So these are both possible in many contexts:

• Ja ću donijeti salatu i kruh
• Ja donijet ću salatu i kruh is not the normal version
• Donijet ću salatu i kruh is normal

And similarly:

• Moja teta će poslužiti juhu
• Moja teta poslužit će juhu is also possible, though often less neutral in tone

For learners, ću + infinitive is a very safe and clear pattern to recognize.

Because Croatian has no articles like English a/an/the.

So nouns appear without an article:

• juhu can mean the soup or just soup
• salatu can mean the salad or a salad
• kruh can mean the bread or just bread

The exact meaning comes from context, not from a separate word like the.

Because Croatian, like English, can use one verb for multiple coordinated objects.

So:

• donijeti salatu i kruh = to bring salad and bread

The single verb donijeti applies to both nouns:

• salatu
• kruh

There is no need to repeat the verb unless you want special emphasis.