Intervju počinje u deset.

Počinje means starts or begins.

Grammatically, it is the 3rd person singular present tense form, and it matches the singular subject intervju.

So:

• intervju = interview
• počinje = starts / begins
• u deset = at ten

That is why the whole sentence means The interview starts at ten.

Because Serbian, like English, often uses the present tense for scheduled future events.

Compare English:

• The interview starts at ten.
• not only The interview will start at ten.

Serbian works the same way:

• Intervju počinje u deset. = a normal way to talk about a scheduled event
• Intervju će početi u deset. = also possible, more explicitly future

So the present tense here does not mean it is happening right now. It means this is the planned start time.

For clock times, Serbian normally uses u + a time expression:

• u deset = at ten
• u pet = at five
• u osam sati = at eight o’clock

So u is the usual preposition for at when giving a specific time.

In this kind of time expression, u takes the accusative.

So u deset is structurally at ten with deset in the accusative.
However, with the number deset, the form looks the same, so you do not see a visible ending change.

That means:

• functionally: accusative
• form: still deset

Because Serbian has no articles.

So Serbian does not have direct equivalents of English the and a/an in normal usage.

That means intervju can mean:

• the interview
• an interview

The exact meaning depends on context.
In this sentence, English naturally translates it as the interview.

The form počinje comes from the verb počinjati, which means to begin / to start and is the imperfective verb.

Its common perfective partner is početi.

A useful way to think of the pair is:

• počinjati = to be starting / to start in an ongoing or repeated sense
• početi = to start / to begin as a completed event

In this sentence, počinje is the normal choice for a scheduled event:

• Intervju počinje u deset. = The interview starts at ten.

Yes. That is also correct.

The difference is mainly style and nuance:

• Intervju počinje u deset. = very natural for schedules, timetables, planned events
• Intervju će početi u deset. = more explicitly future, closer to will start at ten

Both are grammatical. In everyday speech, the version with počinje is very common.

Yes. Serbian word order is fairly flexible.

The most neutral version is:

• Intervju počinje u deset.

But you can also say:

• U deset počinje intervju.

That version puts more emphasis on the time.

So both are possible, but the original sentence is the most straightforward, neutral order for a learner.

Yes, absolutely.

Both are correct:

• u deset
• u deset sati

The version without sati is very common because the meaning is already obvious.
Adding sati just makes it more explicit: at ten o’clock.

Intervju is normally treated as a masculine noun in Serbian.

For example, you would typically say:

• ovaj intervju = this interview
• dobar intervju = a good interview

In your sentence, you do not directly see the gender on the noun itself, but the noun is singular, and the verb počinje is also singular.

A rough pronunciation is:

• Intervju ≈ in-ter-vyoo
• počinje ≈ po-CHEE-nye
• u ≈ oo
• deset ≈ DEH-set

Two useful Serbian spelling points here:

• č sounds like ch in church
• nj sounds like ny in canyon

So počinje has that ny sound in the last part.

In Serbian Cyrillic, it is:

Интервју почиње у десет.