Za ovaj projekt ne dobivamo plaću, nego mali honorar.

Because za here means for, and in this meaning it takes the accusative case.

• ovaj projekt = accusative singular
• projekt is a masculine inanimate noun

For masculine inanimate nouns, the accusative usually looks the same as the nominative, so:

• nominative: ovaj projekt
• accusative: za ovaj projekt

If the noun were masculine animate, you would see a different form, for example:

• za ovog čovjeka = for this man

Croatian often leaves out subject pronouns when the verb ending already shows who the subject is.

Here, dobivamo ends in -mo, which tells you the subject is we.

So:

• ne dobivamo = we do not get / we are not receiving

You could say mi ne dobivamo, but mi would add emphasis, like we don’t get...

Dobivamo is the present tense of the imperfective verb dobivati.

It is used for:

• ongoing situations
• repeated situations
• general arrangements

So in this sentence it means something like:

• we do not receive
• we are not getting
• we don’t get

That fits the idea of how payment for the project works in general.

This is a classic Croatian aspect pair:

• dobivati = imperfective, focuses on the process or repeated receiving
• dobiti = perfective, focuses on receiving something as a completed event

In this sentence, the imperfective dobivamo is natural because the speaker is describing a general payment arrangement.

A perfective present form would usually not work the same way here, because perfective present in Croatian often has a future or completed-event sense rather than a plain ongoing present.

Plaću is the accusative singular of plaća.

• nominative: plaća = salary
• accusative: plaću

It is in the accusative because it is the direct object of dobivamo:

• dobivamo plaću = we receive a salary

For many feminine nouns ending in -a, the accusative singular ends in -u.

They are both types of payment, but not the same kind.

• plaća = salary, regular pay from a job
• honorar = fee, honorarium, payment for a specific task/project, often not a regular salary

So the sentence contrasts:

• not a proper salary
• but a small project fee

That is why honorar is a good choice here.

Because Croatian normally uses ne ... nego ... for the pattern:

• not X, but rather Y

So:

• ne dobivamo plaću, nego mali honorar
• we do not get a salary, but rather a small fee

Ali also means but, but nego is the usual word when the second part replaces or corrects something that was negated in the first part.

Because honorar is also a direct object here, so it is in the accusative singular.

Since honorar is masculine inanimate, its accusative singular looks like the nominative:

• nominative: mali honorar
• accusative: mali honorar

If it were a masculine animate noun, you would see a different form.

That would change the meaning.

• mali honorar = a small fee
• malo honorara = little fee / only a small amount of fee

So mali honorar treats it as a specific fee payment, while malo honorara sounds more like an amount or quantity. In this sentence, mali honorar is the natural choice.

Croatian word order is fairly flexible, and the beginning of the sentence often shows the topic or context.

By putting za ovaj projekt first, the speaker is setting the frame:

• as for this project
• for this project

So the sentence first tells you what situation is being discussed, and then explains the payment.

A different order is possible, for example:

• Ne dobivamo plaću za ovaj projekt, nego mali honorar.

That is still correct, but the emphasis is a little different.

Because nego introduces a contrast or correction, and Croatian normally uses a comma before it in this kind of structure.

So:

• ne X, nego Y

is normally written with a comma:

• ne dobivamo plaću, nego mali honorar

This is standard Croatian punctuation.