Čim završim posao, odmah ću te pozvati.

Čim means as soon as.

It introduces a time clause:

• Čim završim posao = as soon as I finish work / the job

It usually suggests that the second action happens immediately after the first one.

Because Serbian uses the present tense of a perfective verb after time words like čim when talking about the future.

• završim = 1st person singular present of završiti, a perfective verb
• perfective = the action is seen as completed

So:

• Čim završim posao... literally looks like As soon as I finish the job...
• but it refers to a future completed action

Why not the others?

• završavam is imperfective, so it focuses more on the process or repeated action
• završiću is future tense, but after čim Serbian normally does not use future here

So Čim završim posao is the natural pattern.

Because Serbian often drops subject pronouns when the verb already makes the person clear.

Here, the forms already show I:

• završim = I finish
• ću = I will

So ja is unnecessary unless you want emphasis or contrast:

• Ja ću te pozvati = I’ll call you with extra emphasis, maybe contrasting with someone else

This is very normal in Serbian.

Posao means work or job, depending on context.

In this sentence, it is the direct object of završim, so it is in the accusative case.

But for a masculine inanimate noun, accusative singular is often the same as nominative singular, so:

• nominative: posao
• accusative: posao

That is why the form does not change.

Because Serbian has no articles.

English must choose between things like:

• work
• the job
• my work

Serbian often leaves that to context:

• završim posao can mean finish work, finish the job, or sometimes finish my work, depending on the situation

If you want to be more specific, Serbian can add something:

• završim svoj posao = finish my job / my work
• završim taj posao = finish that job

Yes, čim already implies quick sequence, but odmah adds extra emphasis: right away / immediately.

So the sentence feels stronger:

• Čim završim posao, pozvaću te. = As soon as I finish work, I’ll call you.
• Čim završim posao, odmah ću te pozvati. = As soon as I finish work, I’ll call you right away.

You can omit odmah, but keeping it sounds very natural.

This is the Serbian future tense.

It is made with:

• a short form of hteti = to want / will
• plus the infinitive

Here:

• ću = I will
• pozvati = to call

So:

• ću pozvati = I will call

And with the object pronoun:

• ću te pozvati = I will call you

A very common alternative is the attached future form:

• pozvaću te

That means the same thing.

Te means you, specifically:

• accusative singular
• informal

It is the unstressed object form of ti.

So:

• pozvati te = to call you

If you were speaking to more than one person, or using formal you, you would use vas instead:

• Pozvaću vas. = I’ll call you / I’ll call you all.

Because te is a clitic: a short, unstressed word that has a fixed position.

In Serbian, clitics usually go near the beginning of the clause, and in a future construction like this they normally appear before the infinitive:

• odmah ću te pozvati

This is much more natural than trying to place te later.

So the order is:

• odmah = first stressed word
• ću te = clitic cluster
• pozvati = infinitive

Serbian word order is flexible, but clitics like ću and te follow special placement rules.

Not always.

Pozvati can mean several things, depending on context:

• to call
• to invite
• to summon

In this sentence, the most natural meaning is call you, often understood as a phone call or contacting someone.

If you want to make the phone meaning more explicit, Serbian often uses nazvati:

• Čim završim posao, odmah ću te nazvati.

That is very clearly I’ll call you on the phone.

Yes, you could, but the nuance changes.

• čim = as soon as
• kad / kada = when

So:

• Čim završim posao... strongly suggests immediacy
• Kad završim posao... is more neutral: when I finish work...

Since this sentence also has odmah, čim fits especially well.

Yes, you can change the order.

For example:

• Čim završim posao, odmah ću te pozvati.
• Odmah ću te pozvati čim završim posao.

Both mean essentially the same thing, but the emphasis shifts a little:

• starting with Čim završim posao highlights the condition in time
• starting with Odmah ću te pozvati highlights the promise to call

About the comma:

• when the subordinate clause comes first, Serbian normally uses a comma
  
  • Čim završim posao, odmah ću te pozvati.
• when it comes after the main clause, the comma is usually omitted
  
  • Odmah ću te pozvati čim završim posao.

So the comma here is completely normal.