Í flutningabílnum berum við borðið og stöflum kössunum.

This is because Icelandic is a verb-second language in main clauses.

If the sentence begins with something other than the subject, the finite verb usually comes next, and the subject follows it.

So:

• Við berum borðið ... = We carry the table ...
• Í flutningabílnum berum við borðið ... = In the moving truck, we carry the table ...

The fronted phrase Í flutningabílnum sets the scene, and that pushes berum into second position.

No. It is still a normal statement.

For an English speaker, verb + subject may look like a question, but in Icelandic that word order is very common in statements when another element comes first.

So here:

• Í flutningabílnum = first element
• berum = second-position verb
• við = subject

That is completely regular declarative word order in Icelandic.

Because í can take different cases depending on meaning:

• accusative for movement into
• dative for location in

Here the meaning is location: the action is happening in the moving truck, not motion into the truck.

So Icelandic uses the dative:

• í flutningabílnum = in the moving truck

A useful comparison:

• í bílinn = into the car/truck
• í bílnum = in the car/truck

It is a compound noun plus a case ending and the definite article.

You can break it down like this:

• flutninga- = relating to moving/transport
• bíll = car, truck
• -num = dative singular definite ending here

So flutningabílnum means the moving truck in the dative singular.

Icelandic often attaches the to the end of the noun instead of using a separate word.

Both are 1st person plural present tense forms:

• berum = we carry
• stöflum = we stack

The subject is við = we.

Dictionary forms:

• að bera = to carry
• að stafla = to stack

So the sentence has two coordinated verbs with the same subject: we carry ... and stack ...

This is a common Icelandic sound change called u-umlaut.

When a u appears in the following syllable, a in the stem often changes to ö. That is why:

• stafla → stöflum

This kind of vowel change is very common in Icelandic inflection, so it is something learners get used to seeing.

Borðið is the definite singular form of borð.

Here it is the direct object of berum, and bera takes the accusative.

So:

• borð = a table
• borðið = the table

Because borð is a neuter noun, its nominative and accusative singular forms look the same. The -ið is the suffixed definite article.

Kössunum is the dative plural definite form of kassi.

That happens because stafla takes the dative for the thing being stacked.

So:

• kassi = a box
• kössum = boxes, dative plural
• kössunum = the boxes, dative plural definite

The change from a to ö is again due to umlaut, just as in stafla → stöflum.

Because different Icelandic verbs can govern different cases.

In this sentence:

• bera takes the accusative → borðið
• stafla takes the dative → kössunum

English usually just uses word order for direct objects, but Icelandic often shows the relationship through case as well. So two objects in the same sentence can easily have different case forms if they belong to different verbs.

Because the same subject applies to both verbs.

So:

• berum við borðið og stöflum kössunum

means:

• we carry the table and stack the boxes

Icelandic, like English, does not need to repeat the subject when two verbs are joined by og and have the same subject. You could repeat it in some contexts for emphasis, but normally you do not.