Við lærum þetta ekki allt í einu.

A simple breakdown is:

• Við = we
• lærum = learn; this is the 1st person plural form of læra
• þetta = this; it is the direct object
• ekki = not
• allt í einu = all at once, in one go

So the structure is basically:

We + learn + this + not + all at once

That word order is normal Icelandic.

Læra is the dictionary form, meaning to learn.

In the sentence, the verb has to agree with við = we, so Icelandic uses the 1st person plural present form:

• ég læri = I learn
• þú lærir = you learn
• hann/hún/það lærir = he/she/it learns
• við lærum = we learn
• þið lærið = you learn
• þeir/þær/þau læra = they learn

So við lærum means we learn.

Normally, yes, you say við.

Unlike some languages such as Spanish or Italian, Icelandic usually does not drop subject pronouns in ordinary speech and writing. Even though lærum clearly shows we, við is still normally present.

So:

• Við lærum þetta ekki allt í einu = normal
• Leaving out við would usually sound incomplete outside special contexts

Here þetta is the direct object of lærum, so it is in the accusative.

The verb læra commonly takes an accusative object.

The reason this may not look obvious is that þetta is a neuter singular form, and in neuter singular, nominative and accusative are often identical.

So even though the form is þetta, its job in the sentence is still accusative object.

A useful comparison:

• þetta can be nominative or accusative
• the syntax tells you which one it is

This is a very common Icelandic pattern.

In simple terms, short object pronouns and pronoun-like words often come before sentence adverbs like ekki. So:

• Við lærum þetta ekki = natural
• Við lærum ekki þetta = possible, but more marked, often sounding contrastive, as if you mean not this

This is related to a feature often called object shift.

So in your sentence, þetta comes before ekki because that is a normal and natural placement for a short pronominal object.

Here allt í einu means all at once or in one go.

It functions as an adverbial expression, not as a literal sequence you should translate word by word every time.

So the idea is:

• Við lærum þetta ekki allt í einu = we do not learn this in a single step; we learn it gradually

In this sentence, allt í einu belongs together as one expression.

Because einu is the dative singular neuter form of einn = one.

The preposition í can take different cases depending on meaning. In many expressions of state or fixed idiom, it takes the dative. In allt í einu, the expression uses the dative form:

• einu = dative neuter singular

So even if you learn allt í einu as a fixed phrase, it is helpful to know that einu is there for grammatical reasons, not by accident.

Yes, very often.

That is why learners sometimes get confused. The same expression can mean:

• all at once
• suddenly

The context tells you which meaning is intended.

For example:

• Allt í einu byrjaði það að rigna = Suddenly it started to rain

But in your sentence, with ekki and with the idea of learning, the meaning is clearly not all at once, not suddenly.

No, not in this sentence.

Here allt is part of the fixed expression allt í einu. It does not mean all this.

If you wanted to say all this, you would normally say allt þetta.

So there is an important difference between:

• þetta ... allt í einu = this ... all at once
• allt þetta = all this

That distinction helps a lot with understanding the sentence correctly.

A natural way would be:

Við lærum ekki allt þetta í einu.

That sentence is different from the original one:

• Við lærum þetta ekki allt í einu = We do not learn this all at once
• Við lærum ekki allt þetta í einu = We do not learn all this at once

In the second sentence, allt þetta is one noun phrase meaning all this. In the original sentence, allt í einu is an adverbial phrase meaning all at once.

Yes, Icelandic allows some word-order variation for emphasis, but the finite verb in a main clause normally stays in second position.

For example:

• Við lærum þetta ekki allt í einu = neutral
• Þetta lærum við ekki allt í einu = puts more emphasis on þetta

That second version is still normal Icelandic. It just highlights this more strongly.

So Icelandic word order is flexible, but not random.

A helpful approximation for English speakers is:

• þ as in thing
• ð as in this

So:

• þetta starts with the th sound of thin
• Við contains a ð sound roughly like the th in this

The exact Icelandic sounds are not always identical to English ones, but this is a very good starting point for learners.