Við skilum nytjahlutnum inn.

Yes. Skilum is the 1st person plural present form of skila.

• að skila = to return, hand in, deliver back
• við skilum = we return / we hand in

The ending -um is a very common ending for we in the present tense.

So:

• ég skila = I return
• þú skilar = you return
• við skilum = we return

Because it is in the dative singular definite form.

The basic noun is nytjahlutur. In this sentence, it appears as nytjahlutnum because:

1. skila normally takes its thing-object in the dative
2. the noun is definite: the useful object / the utility item

So -num here signals something like to/with/in the dative + the.

A good way to think of it is:

• nytjahlutur = a useful object / utility item
• nytjahlutnum = the useful object / the utility item, in the dative form

This is something Icelandic learners often have to memorize verb by verb.

Many Icelandic verbs require a specific case for their objects. Skila is one of the verbs that commonly takes the dative for the thing being returned or handed in.

In dictionaries and grammar notes, you may see this shown as:

• skila e-u = return/hand in something
  Here e-u stands for einhverju, a dative form meaning something.

So when you learn Icelandic verbs, it is very helpful to learn them together with their case pattern, not just as a bare infinitive.

Here inn is a verb particle, and it adds the idea of in or inward.

With skila, it gives the sense of:

• skila inn = hand in, turn in, return officially

So this is similar to English phrasal verbs like:

• hand in
• turn in
• give back

The word inn is not acting like a normal standalone preposition here. It is part of the verbal meaning.

Because Icelandic often places these little verb particles after the object in a neutral main clause.

So:

• Við skilum nytjahlutnum inn.

has a natural structure of:

• Við = subject
• skilum = finite verb
• nytjahlutnum = object
• inn = particle

This is fairly similar to English patterns like:

• We handed the item in.

where in can come after the object.

Yes. Nytjahlutur is a compound noun.

Icelandic makes a lot of compounds, just like English does. A compound is formed by joining smaller parts into one word. In Icelandic, the last part of the compound is usually the main part grammatically.

That matters because the last element often determines:

• the gender
• the declension pattern

So if you are trying to understand or decline a long noun, it often helps to identify its final element first.

Because Icelandic usually expresses the as a suffix attached to the noun, rather than as a separate word like English does.

So instead of:

• the object

Icelandic often has one word that means object + the.

That is what is happening in nytjahlutnum. The definiteness is built into the noun form itself.

This is one of the biggest structural differences from English.

Við is in the nominative, because it is the subject of the sentence.

Here it means we.

So the basic structure is:

• Við = we, nominative subject
• skilum = return / hand in
• nytjahlutnum = the item, dative object
• inn = in, as a verb particle

The cluster hl is tricky for English speakers.

In modern Icelandic, hl is usually pronounced as a kind of voiceless l. A simple learner-friendly approximation is:

• say an l sound
• but let a little breath come out with it

So hl is not pronounced like English h + l separately in a strong way. It sounds more like a breathy or devoiced l.

If you cannot produce that exactly at first, a plain l is a reasonable beginner approximation, but it is good to notice that native pronunciation is different.

No, not in this sentence.

Skilum here comes from skila, not skilja.

That is a very common confusion for learners because the words look similar.

• skila = return, hand in
• skilja = understand / separate / leave behind, depending on context

So in Við skilum nytjahlutnum inn, the verb is definitely skila.