Jeg må opdatere appen, hvis den ikke virker.

In Danish, modal verbs like må, kan, vil, skal, and bør are followed directly by the infinitive, with no at.

• Jeg må opdatere appen = I have to / must update the app
• Jeg kan hjælpe = I can help

So at is not used after må.

Here, må means something like must, have to, or need to, depending on context.

In this sentence, it suggests necessity:

• Jeg må opdatere appen = I need to update the app

Be aware that må can sometimes also mean may / be allowed to, but in this sentence the meaning is clearly about necessity, not permission.

Because Danish often makes nouns definite by adding the definite ending directly to the noun.

• en app = an app
• appen = the app

This is different from English, which usually uses a separate word like the.

So:

• opdatere appen = update the app

Because app is a common gender noun in Danish, not a neuter noun.

• en app → common gender
• common gender nouns are referred to with den
• neuter nouns (et nouns) are referred to with det

So:

• appen → den

That is why the sentence says hvis den ikke virker.

Virker means works / is working / functions.

It is the present tense of virke.

So:

• den virker = it works
• den ikke virker = it does not work

For apps, devices, systems, and tools, virke is very common when talking about whether something functions properly.

In Danish main clauses, ikke often comes after the finite verb, but in subordinate clauses it usually comes before the finite verb.

Compare:

• Main clause: Den virker ikke. = It doesn’t work.
• Subordinate clause: hvis den ikke virker = if it doesn’t work

Because hvis den ikke virker is a subordinate clause introduced by hvis, the negation ikke comes before virker.

Because subordinate clauses in Danish normally keep a more straightforward subject-before-verb order.

So after hvis:

• hvis den ikke virker

Not:

• hvis virker den ikke

The second version sounds wrong in standard Danish.

A useful rule:

• In a main clause, the verb often comes early because of the V2 rule.
• In a subordinate clause, the subject usually comes before the verb.

In standard Danish writing, a subordinate clause is often separated with a comma.

Here:

• Jeg må opdatere appen, hvis den ikke virker.

The part hvis den ikke virker is a subordinate clause introduced by hvis.

Comma rules in Danish can vary a bit depending on the comma system being used, but learners will very often see a comma before subordinate clauses like this.

Yes, often you can.

• virker = works
• fungerer = functions / works

For an app, both are possible:

• hvis den ikke virker
• hvis den ikke fungerer

Virker is very natural and common in everyday Danish. Fungerer can sound a little more formal or technical in some contexts, but both are correct.

Usually not in this context.

Even though må can sometimes relate to permission, Jeg må opdatere appen, hvis den ikke virker will normally be understood as:

• I need to / must update the app if it doesn’t work

If you want to clearly express permission in Danish, other wording may be better depending on context.

So for this sentence, the natural reading is necessity, not permission.

Yes. Opdatere is a common modern Danish verb, and it is closely related to English update.

Examples:

• Jeg opdaterer appen = I update the app
• Appen skal opdateres = The app needs to be updated

Many technology-related words in Danish resemble English, especially in everyday speech and IT contexts.

Yes, absolutely.

That version is also correct:

• Hvis den ikke virker, må jeg opdatere appen.

When the hvis clause comes first, the main clause changes word order:

• må jeg instead of jeg må

This happens because Danish main clauses follow the V2 rule: the finite verb comes in second position.

So both are correct:

• Jeg må opdatere appen, hvis den ikke virker.
• Hvis den ikke virker, må jeg opdatere appen.

Because Danish forms negation differently from English.

English often uses do-support:

• it does not work

Danish does not do that here. It simply uses:

• subject + ikke
  • verb in the subordinate clause
• den ikke virker

Or in a main clause:

• den virker ikke

So Danish does not need an extra verb like do/does for this kind of negation.