Ég hræri í súpunni með ausu af því að potturinn er svo djúpur.

Because hræri is the 1st person singular present tense form of the verb að hræra.

• að hræra = to stir
• ég hræri = I stir / I am stirring

So the ending -i here matches ég.

In this sentence, Icelandic uses the expression hræra í + dative, which is a very common way to say stir something.

So:

• hræra í súpunni = stir the soup

Even though English does not need a preposition here, Icelandic often does. A good way to remember it is that Icelandic is treating this more like stir in the soup.

Súpunni is dative singular definite.

Breakdown:

• súpa = soup
• súpunni = the soup

It is dative because of the preposition í in this expression. With í, Icelandic often distinguishes:

• accusative for motion into
• dative for being in a place or state

Here there is no movement into the soup; the stirring is happening in it, so dative is used.

That ending includes the suffixed definite article, which is how Icelandic usually says the.

So:

• súpa = soup
• súpan = the soup
• súpunni = to/in/with the soup, depending on case and context

In this sentence, the form needed is dative singular definite, so you get súpunni.

Because með takes the dative case, and ausa is a feminine noun.

So:

• ausa = ladle
• með ausu = with a ladle

This tells you the instrument used to do the action.

It is a noun here: ausa = ladle.

That can confuse learners because there is also a verb að ausa, meaning something like to ladle out / scoop out / pour out with a ladle.

But in með ausu, it is clearly the noun, because it comes after með and means with a ladle.

Because it means with a ladle, not with the ladle.

So the noun is indefinite here:

• með ausu = with a ladle
• með ausunni = with the ladle

English uses a separate word a, but Icelandic often shows definiteness by adding an ending to the noun.

Af því að means because.

You should learn it as a fixed conjunction introducing a reason:

• af því að potturinn er svo djúpur = because the pot is so deep

You may also hear or see related forms like því að or vegna þess að, which can also mean because.

Because potturinn is the subject of er.

• potturinn = the pot, nominative
• pottinn = the pot, accusative

Since the sentence says the pot is so deep, the pot is the thing being described, so it stays in the nominative.

Because Icelandic adjectives agree with the noun they describe in gender, number, and case.

Here the noun is:

• potturinn = masculine, singular, nominative

So the adjective must match:

• djúpur = masculine singular nominative

That is why you get:

• potturinn er svo djúpur = the pot is so deep

Here svo means so.

So:

• svo djúpur = so deep

It often adds emphasis. In many contexts, svo can feel like so, very, or to such a degree depending on the sentence.

Because af því að introduces a subordinate clause, and subordinate clauses usually do not follow the main-clause verb-second pattern in the same way.

So in the main clause you get:

• Ég hræri í súpunni með ausu

But after af því að, the clause has the more regular order:

• potturinn er svo djúpur

That subject-before-verb order is normal here.

Yes. Icelandic has a few common ways to say because.

For example:

• af því að
• því að
• vegna þess að

All can introduce a reason, though the exact tone and frequency may vary by context and speaker. In your sentence, af því að is completely natural.

No. Í can take either accusative or dative, depending on meaning.

A useful rule is:

• accusative = motion into
• dative = location in

Examples:

• Ég fer í húsið = I go into the house
• Ég er í húsinu = I am in the house

In hræri í súpunni, the idea is not movement into the soup, but action happening within it, so dative is used.