Prodavac će pomoći kupcu.

Because pomoći (to help) takes the dative case in Serbian.

• kupac = buyer/customer in the nominative form
• kupcu = to the buyer/customer in the dative singular

So in this sentence:

• Prodavac = the seller, subject
• će pomoći = will help
• kupcu = to the customer

This is a very important pattern to remember: pomagati / pomoći + dative.

Because Prodavac is the subject of the sentence, and subjects are normally in the nominative case.

Here, prodavac is the one doing the action, so it stays in its dictionary form:

• prodavac = seller
• kupcu = to the customer

So the sentence structure is basically:

• Prodavac = who?
• će pomoći = will help
• kupcu = to whom?

Će is the clitic form of the verb hteti (to want), and it is used to form the future tense.

The pattern is:

• ću, ćeš, će, ćemo, ćete, će
  • infinitive

So:

• ja ću pomoći = I will help
• ti ćeš pomoći = you will help
• on/ona/ono će pomoći = he/she/it will help

In your sentence:

• Prodavac će pomoći kupcu. = The seller will help the customer.

Because će is a clitic, and Serbian clitics usually go in the second position of the sentence or clause.

So in:

• Prodavac će pomoći kupcu.

the first element is Prodavac, and the clitic će comes right after it.

This is very typical in Serbian. You will often see future-tense clitics, short pronouns, and forms of jesam placed this way.

For example:

• Marko će doći.
• Sutra ću raditi.
• Kupcu će pomoći prodavac.

All of these follow the same second-position tendency.

In normal standard Serbian, no. That word order sounds wrong because će should not be left at the end like that.

Natural options include:

• Prodavac će pomoći kupcu.
• Kupcu će pomoći prodavac.
• Pomoći će kupcu prodavac.

Serbian word order is flexible, but clitics like će still follow special placement rules.

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

So:

• prodavac can mean a seller or the seller
• kupcu can mean to a customer or to the customer

The exact meaning depends on context.

That is why Prodavac će pomoći kupcu. can be understood as:

• The seller will help the customer
• A seller will help a customer

depending on the situation.

Both mean to help, but they differ in aspect.

• pomagati = imperfective
• pomoći = perfective

In future tense, pomoći often suggests a single, complete act of helping, which fits a sentence like this very well:

• Prodavac će pomoći kupcu. = The seller will help the customer.

If you used pomagati, it could sound more like repeated, ongoing, or habitual helping, depending on context.

This aspect difference is one of the most important features of Serbian verbs.

A useful approximate pronunciation is:

• će ≈ soft cheh
• pomoći ≈ po-MO-chee

A few details:

• ć is softer than English ch
• č and ć are different sounds in Serbian
• pomoći is stressed roughly on MO

So:

• Prodavac će pomoći kupcu ≈ pro-DA-vats cheh po-MO-chee KOOP-tsoo

That is only an approximation, but it helps as a starting point.

Because Serbian often omits subject pronouns when they are not needed.

The verb form and the noun already make the subject clear:

• Prodavac će pomoći kupcu.

Since prodavac is explicitly stated, there is no need to add on.

In fact, adding on would usually only be done for emphasis or contrast:

• On će pomoći kupcu, ne neko drugi. = He will help the customer, not someone else.

Yes. Kupac often covers both buyer and customer, depending on context.

So kupcu here could be understood as:

• to the customer
• to the buyer

In a shop context, customer is often the most natural translation. In another context, buyer may fit better.

Yes, but they are not exactly the same form.

• prodavac is a common noun meaning seller/salesman/shop assistant
• prodavač also exists and is related in meaning, but prodavac is the more usual general form in many contexts

For a learner, prodavac is the safer word to remember first.

Also note the spelling difference:

• c
• č

These are different letters and different sounds in Serbian.