Ég skil ekki allt.

• Ég = I
• skil = understand
• ekki = not
• allt = everything / all of it

So word-for-word, it is roughly I understand not everything, but in natural English that is I don’t understand everything.

Skil is the 1st person singular present tense form of the verb að skilja, which means to understand.

A few present-tense forms are:

• ég skil = I understand
• þú skilur = you understand
• hann/hún/það skilur = he/she/it understands

So in this sentence, ég skil means I understand.

In Icelandic, ekki usually comes after the finite verb in a normal main clause.

So:

• Ég skil ekki allt = correct
• Ég ekki skil allt = not natural/incorrect

This is a very common Icelandic pattern:

• Ég tala ekki íslensku = I do not speak Icelandic
• Hann kemur ekki = He is not coming

English uses do not before the main verb, but Icelandic usually just places ekki after the conjugated verb.

Allt is the neuter singular form of allur, meaning all or everything.

Here it is being used on its own, not before a noun, so it means something like:

• everything
• all of it
• the whole thing, depending on context

So Ég skil ekki allt means I don’t understand everything or I don’t understand all of it.

Icelandic words change form depending on gender, number, and case.

The base word is allur:

• masculine: allur
• feminine: öll
• neuter: allt

In this sentence, allt is used in a general sense meaning everything, and that is normally expressed with the neuter singular form.

So allt is the expected form here.

It is in the accusative, because it is the direct object of skil.

The verb að skilja usually takes an object in the accusative:

• Ég skil þetta = I understand this
• Ég skil hann = I understand him
• Ég skil allt = I understand everything

In this particular word, the neuter singular nominative and accusative forms are both allt, so the form looks the same either way.

No, not exactly.

Ég skil ekki allt usually means:

• I don’t understand everything
• I understand some of it, but not all of it

If you want to say I don’t understand anything, Icelandic would more naturally use:

• Ég skil ekki neitt

That is a very important difference:

• ekki allt = not everything
• ekki neitt = nothing / anything ... not

Usually, no.

In Icelandic, subject pronouns are normally expressed, even when the verb ending already shows who the subject is.

So you would normally say:

• Ég skil ekki allt

Leaving out ég would usually sound incomplete unless the context is very special, such as notes, diary style, or poetic language.

Ég skil ekki allt is the normal neutral order.

You can change word order in Icelandic for emphasis or style, but then the sentence may sound more marked, literary, or emotional.

For example:

• Ekki skil ég allt can sound like It’s not everything that I understand or I certainly don’t understand everything

A learner should usually stick with:

• Ég skil ekki allt

A rough learner-friendly guide is:

yeg skil ehk-ki alt

A few notes:

• Ég begins with a sound like ye- in many modern pronunciations.
• skil has an i like in sit, but longer/clearer depending on speech.
• ekki has a clear k-k sound.
• allt ends with -lt, though the exact pronunciation can vary a bit in connected speech.

If you want to sound more natural, listen carefully to native audio, because Icelandic pronunciation often differs from what the spelling first suggests.

No. Að skilja is a general verb meaning to understand.

It can be used for:

• understanding words or language
• understanding an idea
• understanding a situation

Examples:

• Ég skil íslensku = I understand Icelandic
• Ég skil þetta ekki = I don’t understand this
• Ég skil ekki af hverju = I don’t understand why

So in Ég skil ekki allt, it can refer to language, an explanation, a situation, or anything else that fits the context.