Ég á þrettán ný skilaboð í símanum og fjórtán tölvupósta sem ég á eftir að lesa.

The two á forms both come from the verb eiga, but they are doing different jobs.

• The first á means have:
  Ég á þrettán ný skilaboð ... og fjórtán tölvupósta = I have thirteen new messages ... and fourteen emails
• The second á is part of the fixed expression eiga eftir að + infinitive, which means to still have left to do something or to have yet to do something.

So the second á is not just repeating have in the ordinary possession sense.

Að eiga eftir að lesa means to still have to read, to have left to read, or to have yet to read.

It implies that the reading has not happened yet and that it is still an unfinished task.

So:

• Ég á eftir að lesa tölvupóstana = I still have to read the emails
• It is stronger than just saying something will happen in the future; it specifically points to something remaining undone.

Here að is the infinitive marker, like English to.

So:

• lesa = read
• að lesa = to read

The construction eiga eftir að is followed by an infinitive, so að lesa is exactly what you expect after it.

Because Icelandic and English do not use prepositions in exactly the same way.

For content stored inside a device, Icelandic very naturally says í símanum:

• skilaboð í símanum
• myndir í símanum
• númer í símanum

Even though English often prefers on my phone, Icelandic commonly uses í here. So this is something you should learn as an idiomatic difference, not translate word for word.

Símanum is a declined form of sími (phone).

Two things are happening:

1. í takes the dative when it means location: in the phone
2. Icelandic usually adds the definite article (the) to the end of the noun instead of using a separate word

So:

• sími = a phone
• símanum = the phone in the dative singular

That is why there is no separate word for the.

Icelandic often leaves out possessive words like my, your, or his/her when the meaning is already obvious from context.

Here, if the speaker says:

• Ég á ... skilaboð í símanum

people will naturally understand that it means in my phone, unless there is some reason to think otherwise.

You can say í símanum mínum, but that sounds more explicit and is often used when you want to emphasize or contrast:

• í símanum mínum, ekki þínum

Because ný has to agree with skilaboð.

Skilaboð is neuter plural, and here it is indefinite, so the adjective takes the strong neuter plural form:

• ný

That is why you get:

• ný skilaboð = new messages

Compare:

• nýr = masculine singular
• nýtt = neuter singular
• nýja = often weak/definite forms or other case/gender combinations

So ný is the correct agreement form here.

Skilaboð is normally used as a plural noun.

That means learners should usually think of it as a word that appears in plural form, even in cases where English might say a message or messages depending on context.

That is also why the adjective is plural:

• ný skilaboð

So in this sentence, skilaboð is definitely plural.

Because tölvupóstur is the dictionary form, but in the sentence the noun is:

• plural
• the direct object of á

So it appears in the accusative plural:

• tölvupóstur = nominative singular
• tölvupósta = accusative plural

This is a useful contrast with skilaboð, whose plural form does not visibly change the same way here.

Normally, no. Þrettán and fjórtán are usually treated as indeclinable in everyday use.

So unlike einn, tveir, þrír, and fjórir, they do not usually change their form to match gender or case.

That is why you simply get:

• þrettán ný skilaboð
• fjórtán tölvupósta

The noun, not the numeral, shows most of the grammar around it.

Sem introduces a relative clause, like English that, which, or who.

Here:

• fjórtán tölvupósta sem ég á eftir að lesa

means:

• fourteen emails that I still have to read

So sem links the noun tölvupósta to the description that follows.

It most naturally refers only to fjórtán tölvupósta.

That is because the relative clause comes directly after tölvupósta, so the normal interpretation is:

• thirteen new messages in the phone
• and fourteen emails that I still have to read

If the speaker wanted the clause to apply clearly to both groups, Icelandic would usually phrase the sentence differently.