Við höfum gagn af ráðinu.

Yes. Here Við is the pronoun we.

Icelandic við can also be a preposition meaning things like with, by, or against, so learners often notice the ambiguity. In this sentence, though, it is clearly the subject of the verb:

• Við höfum ... = We have ...

So here it is definitely the pronoun.

Höfum is the 1st person plural present tense of hafa (to have).

The verb changes to match the subject:

• ég hef = I have
• þú hefur = you have
• við höfum = we have

So because the subject is við (we), Icelandic uses höfum.

Gagn af is a very common expression meaning benefit from, get use out of, or derive advantage from something.

So although the sentence literally looks something like We have benefit from the advice, the natural meaning is:

• We benefit from the advice
• The advice is useful to us

This is a good example of an Icelandic phrase that is best learned as a unit:

• hafa gagn af einhverju = to benefit from something

Because gagn commonly goes with the preposition af in this expression.

So Icelandic says:

• hafa gagn af einhverju = to have benefit from something

Even if English might use from or sometimes no extra word at all, Icelandic normally uses af here. This is just the standard pattern the noun gagn takes in this meaning.

Because af takes the dative case, and ráðinu is the dative singular definite form of ráð.

The forms are:

• ráð = advice / a piece of advice / counsel
• ráði = to/from advice, in the dative singular
• ráðinu = the advice, in the dative singular

Since the phrase is af ráðinu, the noun after af must be in the dative.

It is built into ráðinu.

In Icelandic, the definite article is usually attached to the end of the noun instead of being a separate word. So:

• ráð = advice / a piece of advice
• ráðið = the advice
• ráðinu = to/from the advice (dative)

So the ending -inu here shows both:

• definiteness (the)
• dative case

Because gagn is being used in a general, abstract way here.

In the expression hafa gagn af ..., gagn usually appears as a bare noun, much like abstract nouns in English such as use or benefit in certain phrases:

• Það er gagn af þessu. = There is benefit/use in this.
• Við höfum gagn af ráðinu. = We benefit from the advice.

Using a definite form like gagnið would usually sound less natural here unless you were talking about some specific, already identified benefit.

The dictionary form is ráð.

It is a neuter noun. Depending on context, ráð can mean several related things, such as:

• advice
• counsel
• solution
• means/resources
• sometimes plan or measure

In this sentence, it most naturally means the advice.

No, this is a very normal Icelandic main-clause word order.

The structure is:

• Við = subject
• höfum = finite verb
• gagn af ráðinu = the rest of the predicate

So the sentence follows the usual Icelandic verb-second pattern. Since the subject comes first, the verb comes right after it:

• Við höfum ...

That is the most straightforward word order.

Yes. This sentence is natural, but Icelandic has other ways to express a similar idea. For example:

• Ráðið kemur okkur að gagni. = The advice is useful to us.
• Við nýtum ráðið. = We make use of the advice.
• Ráðið nýtist okkur. = The advice is useful to us / helps us.

Still, Við höfum gagn af ráðinu is a good standard phrase and worth learning as a set expression.