Jeg har brug for arbejdsro, hvis jeg skal holde fokus på opgaven hele eftermiddagen.

Yes. At have brug for is a very common way to say to need.

• Jeg har brug for arbejdsro = I need peace and quiet to work
• Literally, it is something like I have use for / I have need of

Danish also has at behøve, which can also mean to need, but have brug for is extremely common in everyday speech.

Compare:

• Jeg har brug for hjælp. = I need help.
• Jeg behøver hjælp. = I need help.

Both are correct, but har brug for often sounds especially natural in ordinary conversation.

Arbejdsro is a compound noun:

• arbejde = work
• ro = calm, quiet, peace

So arbejdsro means something like:

• peace and quiet for working
• a calm working environment
• freedom from disturbance while working

It is a very Danish-style compound word. Danish often combines nouns into one word.

Other examples:

• arbejdsdag = workday
• arbejdsplads = workplace
• arbejdsliv = working life

Because Danish normally writes compound nouns as a single word.

So:

• arbejdsro = correct
• arbejds ro = incorrect

This is very different from English, where similar expressions may be written as two words, hyphenated, or one word depending on usage. In Danish, compounds are usually solid single words.

A useful rule: if English might say work + something, Danish often makes one noun out of it.

Because arbejdsro is being used as an uncountable or abstract noun here, much like peace, time, or energy in English.

So Danish says:

• Jeg har brug for arbejdsro.

Not:

• Jeg har brug for en arbejdsro.

That would sound unnatural here.

Compare:

• Jeg har brug for ro. = I need peace/quiet.
• Jeg har brug for tid. = I need time.
• Jeg har brug for hjælp. = I need help.

These are all abstract or uncountable ideas, so no article is needed.

Yes, hvis means if here.

The clause:

• hvis jeg skal holde fokus på opgaven hele eftermiddagen

means:

• if I am going to stay focused on the task all afternoon
• or if I have to keep my focus on the task all afternoon

It introduces a condition: the speaker needs arbejdsro on the condition that they are expected to stay focused for the whole afternoon.

So the logic is:

• I need working peace and quiet
• if I’m going to keep focusing on the task all afternoon

Skal can mean several things depending on context. Here it is not a simple future marker like English will. It suggests necessity, expectation, or what is required.

So:

• hvis jeg skal holde fokus...

is something like:

• if I am to keep focus...
• if I’m going to keep focus...
• if I have to stay focused...

It gives the sentence a sense that maintaining focus all afternoon is something demanded by the situation.

Compare:

• Jeg skal arbejde i morgen. = I have to / am supposed to work tomorrow.
• Hvis jeg skal nå toget, må jeg gå nu. = If I’m going to catch the train, I have to leave now.

So in your sentence, skal helps express what would be necessary.

You can, but holde fokus is a very natural expression.

• holde = hold, keep
• fokus = focus

So holde fokus means keep focus or maintain focus.

A Dane could also say something with fokusere, depending on style and context, but holde fokus is common and idiomatic.

Compare:

• Jeg prøver at holde fokus. = I’m trying to stay focused.
• Det er svært at holde fokus. = It’s hard to maintain focus.

In this sentence, holde fokus fits very well because the idea is about sustaining concentration over time.

Because Danish uses the preposition på after fokus in this kind of expression.

• fokus på noget = focus on something

So:

• holde fokus på opgaven = keep focus on the task

This works much like English focus on.

More examples:

• Vi skal have fokus på kvalitet. = We need to focus on quality.
• Hun har fokus på detaljerne. = She focuses on the details.

This is just a normal prepositional pattern you need to learn with the noun fokus.

Opgaven is the definite form, meaning the task or the assignment.

The base noun is:

• en opgave = a task, an assignment

The definite singular is:

• opgaven = the task, the assignment

So the sentence refers to a specific task already understood from context.

This is very common in Danish. The definite article is usually added as an ending:

• en bil = a car

• bilen = the car

• en opgave = a task
• opgaven = the task

Because Danish often expresses duration directly, without adding a preposition like English sometimes does.

• hele eftermiddagen = all afternoon / the whole afternoon

It means the focus has to continue for that entire period.

Other examples:

• hele dagen = all day
• hele ugen = all week
• hele natten = all night

You do not need a preposition here. It is simply a time expression showing duration.

Because this is a subordinate clause introduced by hvis.

In a main clause, Danish often has verb-second word order:

• Jeg har brug for arbejdsro.

Here the finite verb har comes in the second position.

But in a subordinate clause, Danish normally uses a more straightforward order:

• hvis jeg skal holde fokus...
• if I am to keep focus...

So the order is:

• hvis
  • subject
    • finite verb
      • rest

This is normal for Danish subordinate clauses.

Compare:

• Jeg bliver hjemme, hvis det regner. = I’m staying home if it rains.
• Hun bliver træt, hvis hun arbejder for længe. = She gets tired if she works too long.

Because Danish punctuation normally separates the main clause from the subordinate clause with a comma.

So:

• Jeg har brug for arbejdsro, hvis jeg skal holde fokus...

That comma is standard Danish writing.

Very broadly:

• main clause first
• comma
• subordinate clause after it

You will see this a lot in written Danish, especially before clauses introduced by words like hvis, at, fordi, som, and når.