Við göngum lengra í skóginn á morgun.

Göngum is the 1st person plural present tense form of ganga.

• ganga = to walk
• við göngum = we walk / we are walking

In this sentence, it can also be translated naturally as we go on foot.

Icelandic often uses the present tense for the future when a time expression already makes the future meaning clear.

So:

• Við göngum ... á morgun = We’re walking / We’ll walk ... tomorrow

This is very normal Icelandic. English does something similar in sentences like We’re leaving tomorrow.

Its basic meaning is walk or go on foot.

So in this sentence, the most literal idea is that we are walking farther into the forest tomorrow. Depending on context, English might translate it as walk or sometimes just go, but Icelandic ganga specifically suggests movement on foot.

Lengra means farther or further.

Here it is the comparative form, so it compares the distance with something understood from context:

• langt = far
• lengra = farther / further

In this sentence, lengra modifies the verb idea göngum, so the sense is we walk farther.

Because lengra is functioning as an adverb, not as an adjective.

It describes how far we walk, not what kind of forest it is.

So:

• lengra = farther, modifying göngum
• it does not need to agree with skóginn

If it were describing a noun, then adjective agreement would matter. Here, it is describing the action.

Because Icelandic uses different cases after í depending on whether there is movement or location.

• í + accusative = into somewhere, with movement
• í + dative = in somewhere, location

So:

• í skóginn = into the forest
• í skóginum = in the forest

Since the sentence describes movement into the forest, the accusative skóginn is correct.

The ending -inn is the definite article, meaning the.

Icelandic usually adds the to the end of the noun instead of using a separate word.

So:

• skógur = forest
• skóginn = the forest (here in the accusative singular)

That is why Icelandic does not need a separate word for the before skóginn.

Yes. Á morgun is the normal expression for tomorrow.

It is a fixed phrase, so learners should just memorize it as a unit.

A useful comparison is:

• á morgun = tomorrow
• í morgun = this morning

Those two can be easy to confuse, so it helps to learn them together.

In normal modern Icelandic, yes, you usually keep the subject pronoun.

Even though göngum clearly shows 1st person plural, Icelandic is not a language where subject pronouns are usually dropped in ordinary sentences.

So Við göngum ... is the normal full sentence.

Yes. Icelandic word order is fairly flexible, especially with time expressions like á morgun.

For example, you can also say:

Á morgun göngum við lengra í skóginn.

That still means the same thing. The main difference is emphasis: putting á morgun first highlights tomorrow.

A useful thing to notice is that when something is moved to the front, the finite verb göngum still comes early in the sentence. That is a common Icelandic pattern.