Når først reservedelen kommer, begynder afhjælpningen på serviceværkstedet.

Here først adds the sense of once or as soon as the necessary condition is finally met.

So Når reservedelen kommer is simply when the spare part arrives.

But Når først reservedelen kommer suggests something more like:

• once the spare part arrives
• when the spare part finally arrives
• once we have the spare part

It often implies that this arrival is the thing everything depends on before the next step can happen.

Because Danish has verb-second word order in main clauses.

The sentence begins with the subordinate clause:

• Når først reservedelen kommer

After that, the main clause starts. In a Danish main clause, the finite verb normally comes in second position, so you get:

• begynder afhjælpningen på serviceværkstedet

Structure:

• Når først reservedelen kommer, = fronted subordinate clause
• begynder = finite verb in second position of the main clause
• afhjælpningen = subject

This is very common in Danish:

• Når han kommer, starter mødet.
• Hvis det regner, bliver vi hjemme.

In English, we usually keep normal subject-verb order after the comma, but Danish does not.

Use når when the event is seen as something that will happen or is expected to happen at some point: when.

Use hvis when the event is uncertain or conditional: if.

So in this sentence, når suggests that the spare part is expected to arrive, and once it does, the repair process starts.

Compare:

• Når reservedelen kommer, begynder afhjælpningen.
  = the part is expected to come

• Hvis reservedelen kommer, begynder afhjælpningen.
  = maybe it comes, maybe it does not

Because Danish often uses the definite form where English would say the.

• reservedelen = the spare part
• afhjælpningen = the remedying / the repair work / the rectification
• serviceværkstedet = the service workshop / the repair shop

The definite ending is attached to the noun:

• reservede l
  • -en = reservedelen
• afhjælpning
  • -en = afhjælpningen
• serviceværksted
  • -et = serviceværkstedet

This is normal Danish grammar, not something special about this sentence.

Afhjælpning comes from afhjælpe, which means to remedy, to correct, or to fix a problem.

In this context, afhjælpningen is not very conversational everyday Danish. It sounds more formal, technical, or administrative. In service, warranty, or repair language, it can mean:

• the repair
• the remedial work
• the corrective work
• the rectification

So this is the kind of word you might see in official service language rather than casual speech.

In everyday Danish, people might more often say something simpler depending on context, such as:

• reparationen
• arbejdet
• de går i gang med at reparere den

In Danish, på is often used with places understood as workplaces, institutions, or functional locations.

So på serviceværkstedet means:

• at the service workshop
• at the repair shop

This is similar to other common Danish patterns:

• på skolen
• på hospitalet
• på kontoret
• på værkstedet

Using i would focus more literally on being physically inside the building or room. Here the point is the location as a working place or department, so på is the natural choice.

Yes.

Both verbs are in the present tense:

• kommer
• begynder

But Danish, like English, often uses the present tense for future events when the meaning is clear from context.

So the sentence refers to a future sequence:

• first the spare part arrives
• then the repair work starts

This is completely normal Danish.

It is a subordinate clause introduced by når.

Structure:

• Når = subordinating conjunction
• først = adverb
• reservedelen = subject
• kommer = finite verb

A useful thing to notice is that Danish subordinate clauses can contain adverbs like først before the subject-verb unit without sounding strange. The whole clause sets up the condition or time frame for the main clause.

Yes, it is a common word in technical and repair contexts.

• reserve here has the sense of spare
• del = part

So reservedel literally means spare part.

With the definite ending:

• reservedelen = the spare part

You will often see it in contexts involving cars, appliances, machinery, electronics, and repairs.

Yes. The original sentence sounds somewhat formal or businesslike, especially because of afhjælpningen.

A more everyday version might be:

• Når reservedelen kommer, går værkstedet i gang med reparationen.
• Når reservedelen kommer, begynder de at reparere den på værkstedet.

These feel more natural in everyday speech, while the original sounds like service-report or customer-support language.

Yes, it is a useful pattern.

Når først ... often means:

• once ...
• once ... finally ...
• when ... at last ...

It emphasizes that the first event unlocks the second.

Examples:

• Når først du er i gang, går det hurtigt.
  = Once you get started, it goes quickly.

• Når først de har sagt ja, kan vi planlægge resten.
  = Once they have said yes, we can plan the rest.

So in your sentence, the arrival of the spare part is the key step that makes the next action possible.