Kupoprodaja će početi posle dogovora.

Kupoprodaja literally means purchase and sale or sale transaction. It is a formal/legal/business-style noun, not the most casual everyday word.

In normal speech, people might more often say something simpler depending on context, such as:

• prodaja = sale
• kupovina = purchase/buying
• prodaja i kupovina = sale and purchase

So kupoprodaja is correct, but it sounds more official, like something you might see in a contract, legal text, or business context.

This is the future tense in Serbian.

The pattern here is:

će + infinitive

So:

• će = will
• početi = to begin

Together:

• će početi = will begin

A full set with će looks like this:

• ja ću početi = I will begin
• ti ćeš početi = you will begin
• on/ona/ono će početi = he/she/it will begin
• mi ćemo početi = we will begin
• vi ćete početi = you(pl)/formal will begin
• oni/one/ona će početi = they will begin

In your sentence, the subject is kupoprodaja, which is singular, so će is the correct form.

Because after će, Serbian commonly uses the infinitive in this kind of sentence:

• će početi = will begin

Compare:

• početi = infinitive, to begin
• počne = a present/subjunctive-type form, not used here
• počinje = present tense, begins / is beginning

So:

• Kupoprodaja počinje = The sale begins / is beginning
• Kupoprodaja će početi = The sale will begin

Also, početi is a perfective verb, which is very natural for a future event viewed as a single completed starting point.

Because the preposition posle (after) requires the genitive case.

So:

• basic form: dogovor = agreement, arrangement
• genitive singular: dogovora

That is why you get:

• posle dogovora = after the agreement / after reaching an agreement

This is a very common pattern:

• posle sastanka = after the meeting
• posle ručka = after lunch
• posle škole = after school

So the change is caused by the preposition posle.

It can mean either, depending on context.

Dogovor often means:

• an agreement
• an arrangement
• an understanding
• something people have agreed on

It does not always mean a formally signed legal agreement. It can be quite flexible.

So posle dogovora could mean:

• after an agreement is reached
• after the arrangement is made
• after people come to an understanding

In a business sentence like this one, it may sound a bit more formal, but the noun itself is not necessarily strictly legal.

Yes. Posle and nakon both mean after.

So you could say:

• Kupoprodaja će početi posle dogovora.
• Kupoprodaja će početi nakon dogovora.

Both are correct.

A rough stylistic difference:

• posle is very common and neutral
• nakon can sound a little more formal or written

But in many contexts they are interchangeable.

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

So:

• kupoprodaja can mean sale, the sale, or even a sale transaction
• dogovora can mean agreement, the agreement, depending on context

Serbian relies on context, word order, and situation instead of articles.

That is very normal, and English speakers often notice it early because English requires articles so often.

The given word order is natural:

• Kupoprodaja će početi posle dogovora.

It is the most straightforward way to say it.

But Serbian word order is more flexible than English, so other versions are possible, especially for emphasis:

• Posle dogovora kupoprodaja će početi.
• Kupoprodaja posle dogovora će početi. (possible, but less neutral)

The first alternative puts emphasis on the time expression after the agreement.

Still, the original version is the most neutral and natural for most situations.

It is pronounced roughly like:

koo-po-pro-DAH-ya

A more careful breakdown:

• ku as in coo
• po as in poh
• pro as in proh
• da as in dah
• ja sounds like ya

So:

• kupoprodaja ≈ koo-po-pro-DAH-ya

And:

• početi ≈ PO-che-tee
• posle ≈ POS-leh
• dogovora ≈ do-go-VO-ra

Yes, it is grammatical and natural, especially in a formal or business context.

That said, depending on context, a native speaker might choose a slightly different wording, for example:

• Prodaja će početi posle dogovora.
• Kupoprodaja počinje nakon dogovora.
• Kupoprodaja će uslediti nakon dogovora. (more formal)

Your original sentence sounds fine, especially if the topic is a contract, transaction, or business deal.

Početi is a perfective verb. Its imperfective partner is počinjati.

• početi = to begin, viewed as a complete event/start
• počinjati = to be beginning / to begin repeatedly or in an ongoing sense

In future contexts, Serbian often uses the perfective verb when talking about a single future event:

• će početi = will begin

That is why početi fits very naturally here. The sentence refers to one future start of the transaction, not an ongoing or repeated process.