Hann er enn að venjast sterkum núðlum með hvítlauk.

This is the Icelandic pattern vera að + infinitive, which often shows that something is happening right now or is still in progress.

So Hann er enn að venjast ... means he is still in the process of getting used to it.

A simpler present form like Hann venst ... can also refer to getting used to something, but er að venjast makes the ongoing process clearer.

Here enn means still.

So Hann er enn að venjast ... = He is still getting used to ...

In other contexts, enn can sometimes mean yet, especially in negatives or questions, but here still is the natural meaning.

The -st ending marks a middle-voice/reflexive-type form in Icelandic.

The basic verb is venja, which is more like to accustom or to train someone into a habit.
But venjast means to get used to / become accustomed to.

So:

• venja = to accustom
• venjast = to get used to

This is a very common pattern in Icelandic, where the -st form has its own meaning and is not always translated literally into English.

Because Icelandic does not build this expression the same way English does.

In English, get used to contains the preposition to.
In Icelandic, venjast itself takes an object in the dative case, so no extra preposition is needed.

That is why you get:

• venjast sterkum núðlum

not something like a literal word-for-word version of English get used to.

Because venjast takes the dative case, and both the adjective and noun have to match that.

The dictionary/basic form would be:

• sterkar núðlur = spicy noodles

But after venjast, it changes to dative plural:

• sterkum núðlum

So:

• sterkar → nominative/accusative plural
• sterkum → dative plural
• núðlur → nominative/accusative plural
• núðlum → dative plural

Literally, yes, sterkur often means strong. But with food, it commonly means spicy or hot.

So sterkar núðlur means spicy noodles, not noodles that are physically strong.

This is very similar to how some languages use their word for strong when talking about strong flavors.

Yes. Núðlur is plural, like English noodles.

In this sentence you see the dative plural form:

• núðlum

So:

• núðlur = noodles
• núðlum = to/for/with noodles, depending on grammar and prepositions

The preposition með usually takes the dative when it means with.

So með hvítlauk means with garlic.

The noun is hvítlaukur. Its dative singular form is hvítlauk.
That form happens to look the same as the accusative singular, so the case is not obvious just from the ending, but after með in this meaning, it is understood as dative.

Most naturally, it describes the noodles:

• sterkum núðlum með hvítlauk = spicy noodles with garlic

So the full noun phrase is basically spicy noodles with garlic.

It is not most naturally understood as he is getting used to things with garlic in a broad sense; the phrase is attached to núðlum.

That is a normal and natural position for it in Icelandic.

The sentence structure is:

• Hann = he
• er = is
• enn = still
• að venjast ... = getting used to ...

Putting enn there makes it modify the whole ongoing action: he is still getting used to it.

Word order in Icelandic can shift for emphasis, but this placement is the standard, neutral one.

Not exactly like that.

There is a related expression:

• að venja sig við e-ð = to get oneself used to something

But that construction uses við + accusative, not the dative pattern used by venjast.

So the correct alternative would be:

• Hann er enn að venja sig við sterkar núðlur með hvítlauk.

Compare:

• Hann er enn að venjast sterkum núðlum með hvítlauk.
• Hann er enn að venja sig við sterkar núðlur með hvítlauk.

These are close in meaning, but the grammar is different:

• venjast
  • dative
• venja sig við
  • accusative

Because the sentence is talking about spicy garlic noodles in a general or indefinite way, not a specific already-known set of noodles.

So Icelandic simply uses the bare noun phrase:

• sterkum núðlum með hvítlauk

If you wanted something more definite, Icelandic would mark that differently, often with the suffixed article on the noun or with a more specific context. Here, the indefinite reading is the natural one.