Seinna um kvöldið kom önnur viðvörun í símann minn, en þá vorum við komin heim.

Because Icelandic normally follows a verb-second pattern in main clauses.

Here, Seinna um kvöldið takes the first position. Once that slot is filled, the finite verb kom must come second, and the subject önnur viðvörun comes after it.

So the pattern is:

• Seinna um kvöldið = first slot
• kom = verb in second slot
• önnur viðvörun = subject

If you started with the subject instead, Önnur viðvörun kom seinna um kvöldið would also be grammatical.

Literally:

• seinna = later
• um kvöldið = in the evening / that evening

So Seinna um kvöldið means later in the evening or later that evening.

The preposition um is very common in time expressions and often means something like during or around. In this use, it takes the accusative case, which is why you get kvöldið here.

Because viðvörun is a feminine noun.

The word annar changes form to match the gender, number, and case of the noun it goes with:

• annar = masculine
• önnur = feminine
• annað = neuter

Since viðvörun is feminine singular nominative here, the correct form is önnur.

Yes. That is very common in Icelandic.

The word annar / önnur / annað can mean:

• another
• second

Context tells you which is more natural in English.

So önnur viðvörun could be understood as:

• another warning
• a second warning

In this sentence, another warning is the most natural English choice.

There are two main clues:

1. Word order: Icelandic often puts the verb before the subject because of verb-second word order.
2. Meaning and structure: önnur viðvörun is the thing that came, so it is the subject.

So even though it comes after the verb, it is still the subject of kom.

Because Icelandic often uses accusative after í when there is movement or something entering something.

Here the idea is that the warning came into / onto / to the phone, so you get:

• í símann minn = into/to my phone

If you used í símanum mínum, that would be dative and would describe location inside the phone, not movement into it.

This is part of a very common Icelandic pattern:

• í + accusative = motion into
• í + dative = location in

That is the normal Icelandic pattern.

Icelandic usually says:

• síminn minn = my phone
• símann minn = my phone, accusative

So the noun comes first, and the possessive pronoun comes after it.

A form like minn sími is possible, but it is more marked and often sounds emphatic, contrastive, or more literary.

Here:

• en = but
• þá = then / at that point / by then

So en þá means something like:

• but by then
• but at that point
• but then

In this sentence, by then is especially natural because the second clause describes a state that was already true at that time.

Because vera + kominn expresses a resulting state: the action of arriving had already happened, and the result was that we were already home.

So:

• við komum heim = we came home / we arrived home
• við vorum komin heim = we had arrived home / we were already home

The second version emphasizes that by the time the warning came, the arrival was already completed.

That is why it fits well with þá.

komin is the past participle / adjective-like form of koma in this construction.

Icelandic often uses vera + past participle to describe a state resulting from an action:

• vera kominn heim = to have arrived home / to be home after arriving

So vorum við komin heim is not just a simple past event. It describes the state of already having arrived.

This construction is very common with verbs of movement.

This is a point learners often notice because agreement in Icelandic can look a bit flexible in everyday usage.

In more strictly gender-marked agreement, you may also see forms such as:

• komnir for a masculine or mixed group
• komnar for an all-female group

But komin is also very common with við in modern Icelandic, especially when the sentence does not spell out the gender makeup of the group.

So the safest thing for a learner is:

• recognize vera komin heim as a very common expression
• understand that the participle can vary in form depending on agreement and usage

Because heim and heima are different words.

• heim = home, homeward, to home
• heima = at home

With movement or arrival, Icelandic uses heim:

• koma heim = come home
• vera komin heim = have arrived home

With location, Icelandic uses heima:

• vera heima = be at home

So komin heim is correct because the idea is arrived home, not just were at home.