Hún skrifaði þrettán setningar í ritgerðina áður en hún tók fjórtán mínútna hlé.

Skrifaði is the past tense of skrifa, meaning to write. In this sentence it is the 3rd person singular past, so it matches hún = she.

A useful comparison:

• að skrifa = to write
• hún skrifar = she writes / she is writing
• hún skrifaði = she wrote

So Hún skrifaði ... means She wrote ...

Because setningar is the thing she wrote, so it is the direct object of skrifaði.

With numbers like þrettán = thirteen, Icelandic normally uses the noun in the plural:

• þrettán setningar = thirteen sentences

In this sentence, setningar is in the accusative plural, because it is the direct object. Conveniently, for this noun, the nominative plural and accusative plural look the same.

Usually not in the way the lower numbers do.

For an English speaker, the important pattern is:

• 1–4 often show more agreement with gender/case
• 5 and above are much less changeable in everyday use

So here you simply get:

• þrettán setningar
• fjórtán mínútna

without changing þrettán or fjórtán very much.

Because í can take either the accusative or the dative, and the choice changes the meaning.

A very common rule is:

• í + accusative = movement into / change into
• í + dative = location in

So:

• í ritgerðina suggests adding something into the essay
• í ritgerðinni would suggest something being in the essay

Here the idea is that she wrote sentences into the essay, so accusative is used: ritgerðina.

It is the suffixed definite article, meaning the.

The base noun is:

• ritgerð = essay

Then:

• ritgerðin = the essay, nominative singular
• ritgerðina = the essay, accusative singular

So í ritgerðina means into the essay.

One thing English speakers need to get used to is that Icelandic usually puts the at the end of the noun instead of as a separate word.

Áður en means before in the sense of before something happened.

It introduces a clause:

• áður en hún tók fjórtán mínútna hlé
  = before she took a fourteen-minute break

So the sentence structure is basically:

• She wrote thirteen sentences into the essay
• before she took a fourteen-minute break

Because the sentence has two clauses, and each clause has its own subject:

• Hún skrifaði ...
• áður en hún tók ...

English does this too:

• She wrote ... before she took ...

So the second hún is completely normal. Icelandic does not usually leave it out here.

Tók is the past tense of taka, meaning to take.

This is an important common verb, and it is irregular:

• að taka = to take
• hún tekur = she takes
• hún tók = she took

So hún tók hlé literally means she took a break.

Because taka hlé is a normal Icelandic expression meaning to take a break.

So:

• taka hlé = take a break
• hún tók hlé = she took a break

This works very much like English. Even though take is a very general verb, the whole phrase is idiomatic and common.

This is a measure expression. Literally, it is something like:

• a break of fourteen minutes

In Icelandic, when a time or measure noun describes another noun like this, the time noun is often put in the genitive plural:

• mínútna = of minutes

So:

• fjórtán mínútna hlé = a fourteen-minute break

This is similar in meaning to English fourteen-minute break, but Icelandic builds it differently.

Because it depends on hlé and describes the length of the break.

You can think of it as:

• hlé fjórtán mínútna = a break of fourteen minutes

Here mínútna is the genitive plural of mínúta.

This kind of genitive is very common with measurements, duration, and quantities in Icelandic.

It is singular.

The sentence is talking about one break, not several breaks:

• fjórtán mínútna hlé = one fourteen-minute break

Even though the break lasted fourteen minutes, the noun hlé itself is singular. In this sentence it is the direct object of tók, so it is in the accusative singular. The form happens to look the same as the nominative.

Sometimes in natural English, yes, but grammatically Icelandic is being more specific.

The Icelandic wording suggests into the essay, meaning the sentences were added to it. English often uses in where Icelandic makes a case distinction:

• Icelandic: í ritgerðina = into the essay
• English: often just in the essay

So the natural English translation may be smoother, but the Icelandic grammar is still important to notice.