Hvis mit festtøj ikke er tørt endnu, må jeg tage den blå kjole i stedet.

Hvis means if and introduces a condition.

In this sentence, the condition is:

• Hvis mit festtøj ikke er tørt endnu = if my party clothes are not dry yet

The rest of the sentence tells us what happens in that case:

• må jeg tage den blå kjole i stedet = then I’ll have to take the blue dress instead

So the whole structure is:

• Hvis ... , ...
• If ... , ...

Because after Hvis, Danish uses subordinate clause word order.

In a subordinate clause, the normal pattern is often:

• subject + adverb + verb

So here:

• mit festtøj = subject
• ikke = adverb
• er = verb

That gives:

• mit festtøj ikke er tørt endnu

Compare:

• Main clause: Mit festtøj er ikke tørt endnu
• Subordinate clause: Hvis mit festtøj ikke er tørt endnu

This is a very important Danish pattern:

• in main clauses, ikke usually comes after the finite verb
• in subordinate clauses, ikke usually comes before the finite verb

Because tørt agrees with the noun festtøj, which is a neuter singular noun.

In Danish, adjectives often change form depending on the noun:

• common gender singular: tør
• neuter singular: tørt
• plural / definite: often tørre

Since tøj is neuter, you get:

• tørt tøj = dry clothes

And with the verb at være, the adjective still agrees:

• Mit festtøj er tørt

So tørt is correct because festtøj is grammatically neuter.

Because festtøj is treated as a singular noun in Danish, even though it refers to clothing.

Tøj means clothes/clothing, but grammatically it behaves like a singular mass noun, much like clothing in English.

So you say:

• mit tøj = my clothes
• mit festtøj = my party clothes / my party outfit

You do not say:

• mine festtøj

because mine is for plural nouns.

Here endnu means yet.

So:

• ikke er tørt endnu = is not dry yet

It refers to something expected to happen later. The clothes are still not dry, but they may become dry soon.

A few useful comparisons:

• endnu = yet / still, depending on context
• allerede = already

Examples:

• Jeg er ikke færdig endnu = I’m not finished yet
• Er du færdig allerede? = Are you finished already?

Here må means something like must, have to, or will have to.

So:

• må jeg tage den blå kjole i stedet means I’ll have to take the blue dress instead

It is not mainly about permission here. It expresses necessity caused by the situation.

That is common in Danish:

• Jeg må gå nu = I have to go now
• Vi må vente = We have to wait

Sometimes må can also mean may in the sense of permission, but in this sentence the context clearly suggests necessity.

Yes. Danish often uses tage in situations where English might say put on, wear, or take depending on context.

Here tage den blå kjole means something like:

• put on the blue dress
• go with the blue dress
• wear the blue dress instead

It sounds natural because the speaker is choosing what to wear.

You may also hear:

• tage en kjole på = put a dress on
• have en kjole på = be wearing a dress

So there is a useful difference:

• tage ... på = to put on
• have ... på = to have on / be wearing

In this sentence, på is omitted because tage den blå kjole already works naturally in the context of choosing clothes.

Because the speaker is referring to a specific dress: the blue dress.

den blå kjole is the normal way to say the blue dress in Danish.

With a definite noun plus an adjective, Danish usually uses double definiteness:

• den
  • adjective + noun

So:

• den blå kjole = the blue dress
• det store hus = the big house
• de røde sko = the red shoes

By contrast:

• en blå kjole = a blue dress

That would mean any blue dress, not a particular one.

Because when a noun is definite and has an adjective before it, standard Danish usually uses:

• den/det/de + adjective + noun in indefinite form

So you say:

• den blå kjole

not normally:

• blå kjolen

Compare:

• kjolen = the dress
• den blå kjole = the blue dress

This is a very common Danish pattern and one that English speakers often need time to get used to.

I stedet means instead.

So:

• den blå kjole i stedet = the blue dress instead

It shows that one option replaces another option.

Related expression:

• i stedet for = instead of

Examples:

• Jeg tager te i stedet = I’ll have tea instead
• Jeg tager te i stedet for kaffe = I’ll have tea instead of coffee

Because the sentence begins with a subordinate clause, and that clause is separated from the main clause with a comma.

So the structure is:

• Hvis mit festtøj ikke er tørt endnu, = subordinate clause
• må jeg tage den blå kjole i stedet. = main clause

This comma helps show where the condition ends and the main statement begins.

In written Danish, commas around subordinate clauses are an important part of standard punctuation.