Čim završimo pauzu, krenućemo na vidikovac.

Čim means as soon as. It suggests an immediate next step: one thing finishes, and the next thing starts right away.

So:

• Čim završimo pauzu, krenućemo na vidikovac. = As soon as we finish the break, we’ll head to the viewpoint.

Compared with kad:

• kad = when
• čim = as soon as

You can often use both, but čim is more specific because it emphasizes immediacy.

In Serbian, after words like čim, kad, and some other time expressions, the subordinate clause often uses a present-tense form even when the meaning is future.

So:

• Čim završimo pauzu... literally looks like As soon as we finish the break...
• but it refers to a future situation.

This is normal Serbian grammar. English does something similar:

• As soon as we finish the break, we’ll leave.

  Notice that English also uses finish rather than will finish in that part.

This is mainly about aspect.

• završiti = perfective, meaning to finish / to complete
• završavati = imperfective, meaning to be finishing / to finish repeatedly / to work on finishing

Here the sentence refers to a completed action that must happen before the next one:

• first we finish the break
• then we head out

Because the completion matters, Serbian uses the perfective verb: završimo.

So čim završimo means something like the moment we have finished.

Because pauzu is the direct object of završimo.

The verb završiti takes an object in the accusative case:

• pauza = nominative singular
• pauzu = accusative singular

So:

• završiti pauzu = to finish the break

This is why you see pauzu, not pauza.

Yes, it is understandable and natural. It means to finish the break.

You may also hear related expressions such as:

• završiti pauzu
• završiti s pauzom
• posle pauze
• kad se pauza završi

But završiti pauzu is perfectly fine and straightforward.

Krenućemo is the future tense of krenuti in 1st person plural: we will set off / we will head out.

Serbian future tense is often made with:

• infinitive + short form of hteti

Here:

• krenuti
  • ćemo → krenućemo

When the clitic future ending is attached to an infinitive ending in -ti, the -ti drops:

• krenuti → krenu-
• krenu- + ćemo → krenućemo

Yes. Both are correct:

• krenućemo
• ćemo krenuti

They mean the same thing.

Very roughly:

• krenućemo is the more tightly connected, standard written form
• ćemo krenuti can sound a little more separate or slightly more conversational in some contexts

In this sentence, krenućemo na vidikovac is completely natural.

Because Serbian uses different prepositions depending on how a place is conceptualized.

Here vidikovac means a viewpoint / lookout point, and Serbian normally says:

• ići na vidikovac
• otići na vidikovac
• krenuti na vidikovac

So na is the idiomatic choice.

A useful pattern:

• na + accusative = movement to / onto / toward certain places
• u + accusative = movement into an enclosed space, town, country, building, etc.

A vidikovac is treated as a destination you go to with na.

It is in the accusative singular, because na with movement takes the accusative:

• na vidikovac = to the viewpoint

It looks unchanged because vidikovac is a masculine inanimate noun, and for many masculine inanimate nouns, the accusative singular is the same as the nominative singular.

So:

• nominative: vidikovac
• accusative: vidikovac

That is why there is no visible ending change.

Because the sentence starts with a subordinate clause:

• Čim završimo pauzu, = subordinate clause
• krenućemo na vidikovac. = main clause

In Serbian, when a clause introduced by čim comes first, it is normally separated from the main clause by a comma.

So the comma is standard punctuation here.

Not exactly.

• ići = to go
• krenuti = to start going / to set off / to head out

So krenućemo na vidikovac is not just we will go to the viewpoint, but more specifically we will set off for the viewpoint or we will head to the viewpoint.

It focuses on the start of the movement, which fits well after čim završimo pauzu.