Ég held áfram að lesa textann hægt.

Because halda has more than one common use.

• Ég held að... often means I think that...
• But halda áfram is a fixed expression meaning to continue / to keep going

So in Ég held áfram að lesa..., the word áfram makes it clear that this is halda áfram = continue, not I think.

Halda is the infinitive, meaning to hold / to continue.

After ég, you need the 1st person singular present tense form, which is held:

• að halda = to continue
• ég held = I continue
• við höldum = we continue

So Ég held áfram... is the correctly conjugated form.

Áfram literally means something like onward / forward / on, but in this sentence it is part of the expression halda áfram, which means:

• continue
• keep on
• carry on

So you should learn halda áfram as a unit.

Here að is the infinitive marker, like English to in to read.

After halda áfram, Icelandic normally uses:

• halda áfram að + infinitive

So:

• halda áfram að lesa = continue to read

This að is not the conjunction that here; it is simply introducing the infinitive verb.

Because it names the action that is being continued.

The structure is:

• Ég = subject
• held áfram = finite verb phrase
• að lesa = infinitive phrase telling you what I continue doing

So lesa stays in the infinitive, just like English continue to read.

Because Icelandic usually puts the definite article onto the end of the noun instead of using a separate word.

So textann already means the text in this sentence.

That is very common in Icelandic:

• noun + attached article
• instead of a separate word like English the

Because textann is the form needed for a definite direct object here.

The verb lesa takes its direct object in the accusative, and texti is a masculine noun. So the forms are different depending on case and definiteness.

Useful forms:

• texti = text, a text, the text (dictionary form / nominative indefinite)
• textinn = the text (nominative definite)
• texta = a text (accusative indefinite)
• textann = the text (accusative definite)

Since the text is the object of lesa, Icelandic uses textann.

Yes. Icelandic often uses the neuter singular form of an adjective adverbially.

So:

• hægur = slow (masculine)
• hæg = slow (feminine)
• hægt = slow (neuter)

But hægt can also function as an adverb meaning slowly.

So:

• lesa hægt = read slowly

This is a very common Icelandic pattern.

That word order is natural and neutral in Icelandic.

In a phrase like this, the adverb often comes:

• after the infinitive’s object, or
• later in the verb phrase

So að lesa textann hægt sounds normal and straightforward.

If you move hægt, the sentence may still be possible, but the emphasis or style can change. For a learner, textann hægt is a good standard order to copy.

Yes, you could, but it has a slightly different feel.

• Ég held áfram að lesa textann hægt = I continue / I keep reading the text slowly
• Ég er að halda áfram að lesa textann hægt = I am continuing to read the text slowly

The version with er að emphasizes that the action is happening right now, in progress.

But Icelandic often uses the simple present where English would prefer am ...-ing, so the shorter sentence is very normal.

Yes, definitely.

It is best to learn this as a set pattern:

• halda áfram að + infinitive

Examples:

• Ég held áfram að lesa. = I continue reading.
• Hún heldur áfram að tala. = She keeps talking.
• Við höldum áfram að vinna. = We continue working.

Learning it as one chunk will make it much easier to use correctly.