Poslodavac pregovara o plati.

Because the preposition o usually requires the locative case when it means about / concerning.

• Base form: plata = salary
• Locative singular: plati

So:

• o plati = about the salary

This is a very common pattern in Serbian:

• pričati o poslu = to talk about work
• razmišljati o budućnosti = to think about the future
• pregovarati o plati = to negotiate about salary

Pregovara is the 3rd person singular present tense of pregovarati, which means to negotiate.

So:

• ja pregovaram = I negotiate / am negotiating
• ti pregovaraš = you negotiate
• on/ona/ono pregovara = he/she/it negotiates

In this sentence, poslodavac is singular, so the verb is also singular:

• Poslodavac pregovara = The employer is negotiating

Depending on context, Serbian present tense can correspond to English:

• negotiates
• is negotiating
• sometimes even does negotiate

Grammatically, yes: poslodavac is a masculine noun.

It means employer, and like many Serbian nouns for people, its grammatical gender is masculine in its basic dictionary form. It can still refer to an employer regardless of real-life sex in some contexts, but if you specifically want a feminine form, Serbian can use:

• poslodavka = female employer

In your sentence, poslodavac is the subject, and that is why the verb is:

• pregovara (masculine/singular subject, though present tense itself does not visibly mark gender)

Because Serbian does not have articles like English a/an/the.

So poslodavac can mean:

• an employer
• the employer

And plati can refer to:

• a salary
• the salary

The exact meaning depends on context. In this sentence, English might translate it as either:

• The employer is negotiating about the salary
• An employer is negotiating about salary

Yes, often it can. Serbian frequently uses pregovarati o + locative to express negotiate about / negotiate over / negotiate concerning something.

So:

• pregovarati o plati = to negotiate salary
• literally: to negotiate about the salary

English usually sounds more natural without about, but Serbian normally keeps the preposition:

• o plati
• o uslovima
• o ugovoru

No. Plata is a very common everyday word for salary / pay, especially regular employment income.

Another important word is:

• zarada = earnings / income / pay

And sometimes you may also see:

• plaća = a standard word in Croatian, less usual in Serbian standard

In Serbian, for this sentence, plata is the most natural and expected choice.

Poslodavac is in the nominative singular because it is the subject of the sentence.

So the sentence breaks down like this:

• Poslodavac = subject, nominative singular
• pregovara = verb
• o plati = prepositional phrase, locative singular

This is the normal basic structure of a Serbian sentence.

Yes. Serbian word order is more flexible than English, because cases help show what each word is doing.

The neutral order here is:

• Poslodavac pregovara o plati.

But you could also say:

• O plati pregovara poslodavac.
• Pregovara poslodavac o plati.

These versions may sound more marked or emphasize different parts of the sentence. For a learner, the original order is the safest and most neutral.

Here it is locative singular of plata.

The plural of plata is plate. In the locative plural, you would normally get:

• o platama = about salaries

So:

• o plati = about the salary
• o platama = about salaries

That -i ending here signals a singular locative form of a feminine noun like plata.

Pregovarati is imperfective.

That means it describes an ongoing, repeated, or general action:

• Poslodavac pregovara o plati. = The employer is negotiating / negotiates about salary.

A related perfective verb is often:

• ispregovarati = to negotiate something successfully / to negotiate through to a result

For beginners, the important point is that pregovarati is the normal verb to use for the process of negotiating.

A rough pronunciation guide is:

• po-slo-DA-vats

A few helpful points:

• c in Serbian is pronounced like ts in cats
• the stress is not usually written in normal Serbian spelling
• each letter is pronounced quite consistently

And plati is roughly:

• PLA-ti

So the whole sentence is approximately:

• po-slo-DA-vats pre-go-VA-ra o PLA-ti

Not in the same meaning.

• pregovarati o plati = to negotiate about / over salary
• za platu usually means for a salary / in exchange for a salary

So these are different ideas.

Examples:

• Pregovaraju o plati. = They are negotiating salary.
• Radi za platu. = He/She works for a salary.

So after pregovarati, o + locative is the right structure here.

If you want employers are negotiating about salaries, you would say:

• Poslodavci pregovaraju o platama.

Changes:

• poslodavac → poslodavci = employers
• pregovara → pregovaraju = are negotiating
• plata → platama after o in the locative plural

This is a good way to see how Serbian changes noun and verb forms together.