Želim odmor na moru, jer sada mnogo radim.

In Serbian, the subject pronoun is often omitted because the verb ending already shows the person and number.

• želim = I want
• the ending -m tells you it is 1st person singular

So Želim odmor... is completely natural.
You can say Ja želim..., but that adds emphasis, like I want it.

Želim is the 1st person singular present tense of the verb želeti / željeti (to want).

So:

• ja želim = I want
• ti želiš = you want
• on/ona/ono želi = he/she/it wants

In this sentence, it simply means I want.

Here odmor is the direct object of želim (I want), so it should be in the accusative case.

But odmor is a masculine inanimate noun, and for many masculine inanimate nouns, the accusative singular looks exactly the same as the nominative singular.

So:

• nominative: odmor
• accusative: odmor

That is why the form does not change.

Odmor usually means rest, a break, holiday, or vacation, depending on context.

In this sentence, it most naturally means a vacation / a holiday.

A learner should notice that Serbian often uses one word where English may choose between several options depending on context.

Because after na when it means location, Serbian uses the locative case.

The noun is:

• nominative: more = sea
• locative singular: moru

So:

• na moru = at the sea / by the sea / on the seaside

This is a very common phrase in Serbian.

This is an important vocabulary-and-preposition question.

• na moru means at the seaside / by the sea / on vacation at the coast
• u moru means in the sea

So if you want to say someone wants a seaside vacation, na moru is correct.
If you said u moru, it would sound like being physically inside the water.

Moru is the locative singular of more (sea).

The pattern is:

• nominative: more
• genitive: mora
• dative: moru
• accusative: more
• vocative: more
• locative: moru
• instrumental: morem

In this sentence, it is locative because of na used for location: na moru.

Because jer means because and introduces a subordinate clause.

The sentence has two parts:

• Želim odmor na moru
• jer sada mnogo radim

In standard Serbian punctuation, a clause introduced by jer is separated by a comma.

So the comma here is normal and expected.

Jer means because.

It is one very common way to introduce a reason:

• Želim odmor na moru, jer sada mnogo radim.
• I want a vacation by the sea because I’m working a lot now.

Another common option is zato što:

• Želim odmor na moru zato što sada mnogo radim.

Both are natural.
Jer is short and very common in everyday language.

Sada means now.

Yes, in everyday speech it is very often shortened to sad:

• sada mnogo radim
• sad mnogo radim

Both are common.
Sada may sound a little more full or neutral, while sad is very common in conversation.

Because mnogo means a lot / much, which fits the meaning of working a lot.

• mnogo radim = I work a lot / I am working a lot

Vrlo means very, and it is usually used with adjectives or adverbs, not with a verb in this way.

So:

• mnogo radim = correct
• vrlo radim = not natural here

It can mean either, depending on context.

Serbian present tense often covers both:

• I work
• I’m working

Here, because of sada (now), the sentence strongly suggests a current situation:

• because I’m working a lot now

But in another context, radim could also mean a general habitual action: I work.

Radim is the 1st person singular present tense of raditi (to work).

So:

• ja radim = I work / I am working

Raditi is an imperfective verb, which is the normal choice for an ongoing, repeated, or general activity like working.

Yes, Serbian word order is quite flexible.

The sentence uses a very natural neutral order:

• sada mnogo radim = now I work a lot / I’m working a lot now

But you could also hear:

• mnogo sada radim
• radim mnogo sada
• ja sada mnogo radim

These versions may shift emphasis slightly, but the basic meaning stays the same.

The original order is natural and clear.

Yes. Na moru often corresponds naturally to:

• by the sea
• at the seaside
• on the coast
• seaside vacation

A very literal word-for-word translation does not always sound best in English, so several English phrasings can be correct.

Yes, it is natural and understandable.

It means that the speaker wants a holiday/vacation at the seaside. Serbian commonly uses:

• odmor na moru = vacation at the seaside
• letovanje = summer holiday, often at the sea
• ići na more = to go to the seaside / go to the sea for vacation

So the phrase is fully normal Serbian.

Yes, but it sounds a bit different.

• želim = I want / I would like
• hoću = I want / I will, often stronger, more direct, sometimes more forceful

So:

• Želim odmor na moru sounds neutral and polite.
• Hoću odmor na moru can sound stronger, more insistent: I want a vacation at the seaside!

For a learner, želim is usually the safer choice in neutral situations.