Moram raditi prekovremeno večeras, jer projekt još nije gotov.

Because Croatian often uses a modal verb + infinitive structure, just like English.

• moram = I must / I have to
• raditi = to work

So moram raditi literally means I must work.

Here:

• moram is the conjugated verb
• raditi stays in the infinitive

This is very similar to English I have to work.

Moram is the 1st person singular present tense of morati (to have to, must).

So:

• ja moram = I must
• ti moraš = you must
• on/ona mora = he/she must

Even though Croatian often drops subject pronouns, the ending -am already tells you the subject is I.

After modal verbs like morati (must / have to), Croatian normally uses the infinitive.

So:

• Moram raditi. = I have to work.
• Moram učiti. = I have to study.
• Moram ići. = I have to go.

That is why you get moram raditi, not a second fully conjugated verb.

Prekovremeno means overtime or extra hours beyond normal working time.

In this sentence, it works like an adverb:

• raditi prekovremeno = to work overtime

You may also see related forms such as:

• prekovremeni rad = overtime work
• raditi prekovremene sate = to work overtime hours

In everyday speech, raditi prekovremeno is very common.

Večeras is exactly the normal Croatian word for tonight / this evening in this kind of sentence.

Examples:

• Vidimo se večeras. = See you tonight.
• Radim večeras. = I’m working tonight.

It comes from večer (evening), but večeras is the standard adverbial form meaning this evening / tonight.

Jer means because.

So:

• ..., jer projekt još nije gotov. = ..., because the project is not finished yet.

The comma is standard in Croatian before jer when it introduces a subordinate clause.

That means the sentence is divided into:

1. Moram raditi prekovremeno večeras
2. jer projekt još nije gotov

Projekt is the standard Croatian form.

• Croatian: projekt
• Serbian often: projekat

So in Croatian, projekt is the form you should normally use.

Here još means still or yet, depending on how you translate the whole sentence into natural English.

• još nije gotov = is not finished yet
• literally, it can also feel like is still not finished

This word often expresses continuation:

• Još radim. = I’m still working.
• Još nisam spreman. = I’m not ready yet / I’m still not ready.

Croatian often expresses this idea with:

• nije = is not
• gotov = finished / done / ready

So projekt nije gotov literally means:

• the project is not finished
• or the project is not ready/done

This is a very common pattern in Croatian:

• Ručak je gotov. = Lunch is ready / done.
• Posao nije gotov. = The work isn’t finished.

Gotov agrees with the noun projekt.

Since projekt is:

• masculine
• singular

the adjective/predicate form is gotov.

Compare:

• projekt je gotov = masculine singular
• knjiga je gotova = feminine singular
• pismo je gotovo = neuter singular
• projekti su gotovi = masculine plural

So the ending changes to match the noun.

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

So projekt can mean:

• a project
• the project

You understand which one is meant from context. In this sentence, English naturally says the project, but Croatian just says projekt.

Projekt is in the nominative singular because it is the subject of the clause:

• projekt još nije gotov = the project is not finished yet

The thing that is not finished is projekt, so it stays in the nominative.

Not completely. Croatian word order is more flexible than English, though some versions sound more natural than others.

The given sentence:

• Moram raditi prekovremeno večeras, jer projekt još nije gotov.

is natural and clear.

You could also hear:

• Večeras moram raditi prekovremeno, jer projekt još nije gotov.
• Moram večeras raditi prekovremeno, jer projekt još nije gotov.

These all mean roughly the same thing, but the emphasis changes slightly:

• Večeras first emphasizes tonight
• Moram first emphasizes the obligation

Yes. The most common alternative is zato što.

So you could also say:

• Moram raditi prekovremeno večeras zato što projekt još nije gotov.

Both jer and zato što mean because.

In many situations:

• jer is short and very common
• zato što can sound a bit more explicit or emphatic

The Croatian sentence already covers the normal meaning I have to work overtime tonight very naturally.

Croatian does not always separate these English shades of meaning in the same way. So:

• Moram raditi prekovremeno večeras is the standard way to say it.

If you wanted to stress that it is happening right now / this evening as a current situation, context usually does the job rather than a special tense.

A rough pronunciation guide:

• Moram ≈ MO-ram
• raditi ≈ RA-di-ti
• prekovremeno ≈ pre-ko-VRE-me-no
• večeras ≈ VE-che-ras
• jer ≈ yer
• projekt ≈ pro-yekt
• još ≈ something like yosh
• nije ≈ NEE-ye
• gotov ≈ GO-tov

A very rough full approximation: MO-ram RA-di-ti pre-ko-VRE-me-no VE-che-ras, yer PRO-yekt yosh NEE-ye GO-tov.

A useful breakdown is:

• morati = must, have to
• raditi = to work
• prekovremeno = overtime
• večeras = tonight / this evening
• jer = because
• projekt = project
• još = still / yet
• nije = is not
• gotov = finished / done / ready

If you learn just the core chunks, these are especially useful:

• moram raditi = I have to work
• raditi prekovremeno = work overtime
• još nije gotov = is not finished yet