Ég átta mig á því að ég þarf meiri tíma.

Að átta sig á is an idiomatic expression meaning to realize, to understand, or to become aware of something.

So:

Ég átta mig á því að ég þarf meiri tíma
= I realize that I need more time

Word-for-word, it is not very natural in English. The whole expression should be learned as a unit.

Because átta sig á is a reflexive expression.

The sig part changes to match the subject:

• ég átta mig
• þú áttar þig
• hann/hún/það áttar sig
• við áttum okkur
• þið áttið ykkur
• þau átta sig

So in your sentence, the subject is ég, so the reflexive form is mig.

Here því is a pronoun that points forward to the whole clause that follows.

A very common Icelandic pattern is:

• átta sig á einhverju = realize something
• átta sig á því að... = realize that...

So því is there because the verb expression needs something after á, and then the clause with að explains what that something is.

A good way to think of it is:

• I realize it, that...
• except in natural English we just say I realize that...

No. Here að means that, not to.

In this sentence, að introduces a subordinate clause:

• að ég þarf meiri tíma = that I need more time

So this is not an infinitive marker. It is a conjunction.

Because að ég þarf meiri tíma is a full clause, and it needs its own subject.

So:

• Ég átta mig á því = I realize it
• að ég þarf meiri tíma = that I need more time

Even though English also repeats I here, learners sometimes expect Icelandic to leave it out. But it cannot be omitted in this sentence.

Because meiri has to agree with tíma, and tími is a masculine noun.

Meiri is the comparative form of mikill = much / great.

Here:

• tími = nominative singular
• tíma = accusative singular

Since the noun is masculine singular, the correct form is meiri.

Compare:

• meiri tími = more time
• meira vatn = more water

Vatn is neuter, so it takes meira, not meiri.

Because þurfa takes an accusative object.

The verb is:

• að þurfa = to need

So:

• ég þarf tíma = I need time

Here tíma is the accusative form of tími.

This is very common in Icelandic: the verb determines the case of its object.

No. That would be incorrect.

You need the full pattern:

átta sig á því að...

The preposition á belongs to the expression, and því is normally used before the að-clause.

So learners should use:

Ég átta mig á því að ég þarf meiri tíma

not:

Ég átta mig að...

It has the same spelling, but here it is a completely different word.

• átta = eight
• að átta sig á = to realize / to understand

In your sentence, it is clearly the verb, because it appears in the verbal expression ég átta mig á...

Both are in the present tense.

• ég átta mig = I realize / I am realizing
• ég þarf = I need

So the sentence describes a present realization:

I realize that I need more time

Depending on context, English might also say I’m realizing that I need more time, but I realize is the most straightforward translation.

It breaks down like this:

• Ég = I
• átta mig á því = realize it / become aware of it
• að = that
• ég þarf = I need
• meiri tíma = more time

So the structure is:

I realize that I need more time

A useful pattern to remember is:

Ég átta mig á því að...
= I realize that...