Ég ætla að setja upp gardínurnar í svefnherberginu í kvöld.

Ætla að is a very common way to express intention or what someone is going to do.

So Ég ætla að setja upp... means something like I’m going to put up... or I intend to put up...

A few useful points:

• ætla is the conjugated verb here: Ég ætla = I intend / I’m going to
• að introduces the following infinitive
• setja stays in the infinitive because it depends on ætla að

This construction often sounds more like a planned action than a simple future statement.

Because it comes after ætla að.

In Icelandic, after verbs like ætla að, the next verb is normally in the infinitive:

• Ég ætla að fara = I’m going to go
• Ég ætla að kaupa = I’m going to buy
• Ég ætla að setja upp = I’m going to put up

So setja is not conjugated here because ætla is the main finite verb of the clause.

Setja upp is a verb + particle combination, and together it means put up, install, or hang up, depending on context.

So:

• setja by itself = put, place, set
• setja upp = put up, set up, install

In this sentence, because the object is gardínurnar (the curtains), setja upp means something like hang up / put up the curtains.

The upp is important because it helps create the specific meaning. Without it, the sentence would feel less natural for this idea.

Because gardínurnar means the curtains, while gardínur means just curtains.

Icelandic usually adds the definite article to the end of the noun rather than using a separate word like English the.

Here is the pattern:

• gardína = curtain
• gardínur = curtains
• gardínurnar = the curtains

So the -nar part is the definite article in this plural form.

It is the direct object of setja upp, so it is in the accusative.

The noun gardína is feminine, and in the plural definite the accusative form is:

• gardínurnar

In this particular word, the nominative plural definite and accusative plural definite happen to look the same, so you identify the case from the sentence role rather than from a visible ending change.

Because this means in the bedroom, and after í Icelandic uses different cases depending on whether the phrase describes:

• location = where something is → usually dative
• motion into a place = where something is going → usually accusative

Here, í svefnherberginu describes location: the curtains are being put up in the bedroom, not moved into the bedroom.

So we get the dative singular definite form:

• svefnherbergi = bedroom
• svefnherberginu = the bedroom / in the bedroom

The -nu ending is part of that definite dative form.

Because Icelandic usually has a suffixed definite article.

Instead of a separate word like English the, Icelandic commonly attaches the article to the noun:

• herbergi = room
• herbergið = the room
• gardínur = curtains
• gardínurnar = the curtains

That is one of the basic features of Icelandic nouns. So in this sentence both the curtains and the bedroom are expressed by noun forms with article endings attached.

Í kvöld is a fixed, very common time expression meaning tonight.

It does not need a definite article in Icelandic. You should learn it as a set phrase:

• í dag = today
• í morgun = this morning
• í kvöld = tonight

So even though English uses one word, Icelandic uses the preposition í plus the noun kvöld.

Because they do two different jobs:

• í svefnherberginu = place → in the bedroom
• í kvöld = time → tonight

So even though both begin with í, one is a location phrase and the other is a time expression.

That is completely normal in Icelandic.

The sentence as given is a very natural neutral order:

Ég ætla að setja upp gardínurnar í svefnherberginu í kvöld.

But Icelandic word order is somewhat flexible, especially if you want to emphasize time or place.

For example, you could also say:

Í kvöld ætla ég að setja upp gardínurnar í svefnherberginu.

That puts extra focus on tonight.

One important rule to remember is that Icelandic is a verb-second language in main clauses. If you move something to the front, the finite verb usually comes next:

• Ég ætla...
• Í kvöld ætla ég...

So you cannot just move words around freely in the same way as in English.

Both can refer to the future, but they are not exactly the same.

• Ég ætla að setja upp... = I’m going to put up... / I intend to put up...
  • emphasizes plan or intention
• Ég mun setja upp... = I will put up...
  • often sounds more like a plain future statement, promise, or prediction

In everyday Icelandic, ætla að is extremely common when talking about something you plan to do.

Yes, gardína is a normal and common word for curtain.

You may also see gluggatjöld, which can refer more generally to window curtains or window coverings. Depending on context, both can be natural, but gardína is straightforward and very common for a learner to know.

So gardínurnar here is a perfectly normal choice for the curtains.

Then Icelandic would normally switch to the accusative after í, because the phrase would describe movement into a place rather than location in a place.

Compare:

• í svefnherberginu = in the bedroom → location → dative
• í svefnherbergið = into the bedroom → movement/destination → accusative

That location-vs-motion distinction after í is very important in Icelandic and is something English speakers often need time to get used to.