Þetta er ekki nógu nákvæm skýring; geturðu sagt mér þetta aftur?

Both instances are the same word, but they do different jobs.

• The first Þetta is the subject: Þetta er ekki nógu nákvæm skýring.
• The second þetta is the object of sagt: geturðu sagt mér þetta aftur?

In both places, þetta is the neuter singular form of this. Icelandic often uses it to mean this, this thing, or what was just said.

A useful detail: in neuter singular, the nominative and accusative forms are the same, so þetta looks identical whether it is the subject or the object.

Because that is the normal word order in Icelandic main clauses.

In a simple statement, the finite verb usually comes early, and ekki normally follows it:

• Þetta er ekki... = This is not...

So English speakers should get used to patterns like:

• Ég er ekki...
• Hann kemur ekki...
• Þetta er ekki...

Putting ekki before er would sound wrong here.

Nógu means enough or sufficiently.

When it modifies an adjective, it usually comes before that adjective:

• nógu nákvæm = precise enough
• nógu stór = big enough
• nógu góð = good enough

So:

• ekki nógu nákvæm = not precise enough

English does the same thing in meaning, but the Icelandic word order is worth noticing.

Because the adjective has to agree with the noun skýring.

Skýring is:

• feminine
• singular
• nominative here

So the adjective also appears in the feminine singular nominative form:

• nákvæm skýring

The dictionary form is usually the masculine singular nominative:

• nákvæmur

So learners often see nákvæmur first, but in real sentences the ending changes to match the noun.

For comparison:

• nákvæmur texti — masculine
• nákvæm skýring — feminine
• nákvæmt svar — neuter

Icelandic does not normally use a separate indefinite article like English a/an.

So:

• skýring can mean an explanation or just explanation, depending on context.

If you want the explanation, Icelandic usually adds the definite article to the end of the noun:

• skýringin = the explanation

So here:

• nákvæm skýring = a precise explanation
• nákvæma skýringin would not be the normal way to say the precise explanation

Geturðu is a very common contracted form of getur þú.

• getur = can
• þú = you

So:

• geturðu...? = can you...?

This kind of contraction is very normal in Icelandic, especially in speech and everyday writing.

Also, this is a yes/no question, so the verb comes first:

• Geturðu sagt mér þetta aftur?

That verb-first order is one of the most important things to notice in Icelandic questions.

Because segja usually takes the person being told in the dative.

The pattern is:

• segja einhverjum eitthvað
• to say/tell someone something

So:

• mér = dative of ég
• þetta = the thing being said

That gives:

• segja mér þetta = say this to me / tell me this

Other examples:

• segðu honum þetta = tell him this
• ég sagði henni sannleikann = I told her the truth

This is a very common learner question.

Here, sagt is the non-finite form used with geta in this kind of construction. So the natural pattern is:

• getur sagt
• get ekki gert
• get farið

So:

• Geturðu sagt mér þetta aftur? is the normal phrasing.

A very useful way to learn this is as a chunk:

• geta + sagt
• geta + gert
• geta + farið

By contrast, with some other verbs you may see a different pattern, for example:

• Viltu segja mér þetta aftur? = Would you like to / will you tell me this again?

So yes: English speakers often expect segja, but sagt is the form you want here.

Here aftur means again.

So:

• sagt mér þetta aftur = say this to me again

Putting aftur at the end is very natural. Icelandic often places adverbs like this late in the clause.

You may hear slightly different word orders in real speech, but the version in your sentence is very standard and idiomatic.

These two letters are very important in Icelandic.

• Þ / þ is like the th in thing
• Ð / ð is roughly like the th in this

So:

• Þetta begins with the thing sound
• geturðu contains the ð sound

A few helpful notes:

• Þ can appear at the beginning of words.
• ð does not appear at the beginning of native Icelandic words.
• Icelandic pronunciation is not always exactly the same as English th, but that comparison is a good starting point.

It sounds fairly natural and normal, especially if you are asking someone to repeat or clarify something.

That said, Þetta er ekki nógu nákvæm skýring can sound a bit blunt depending on tone, because it directly says this is not precise enough.

If you want a softer version, you could say things like:

• Geturðu sagt mér þetta aftur? — simpler and less critical
• Gætirðu sagt mér þetta aftur? — a bit softer, like Could you say that again?
• Geturðu útskýrt þetta aðeins betur? — Can you explain this a little better?

So the original sentence is fine, but tone and context matter.