Hun bygger videre på innfallet.

Because videre adds the idea of continuing or developing something further.

• bygge på = to build on, base something on
• bygge videre på = to build further on, continue developing

So videre makes the sentence feel more like she is taking an idea and expanding it, not just referring to it as a base.

Innfallet is the definite form of innfall, a noun that usually means something like:

• a sudden idea
• a whim
• a spontaneous thought
• an impulse of inspiration

Depending on context, innfall can sound a bit more sudden or quirky than a neutral word like idé.

So it is often not just any idea, but a thought that came to someone suddenly.

Because Norwegian usually marks definiteness by adding an ending to the noun.

Here, innfall is a neuter noun:

• et innfall = an idea / a whim
• innfallet = the idea / the whim

So -et is the definite ending for many neuter nouns.

Because bygge videre på is the normal expression. The preposition på belongs to the phrase.

It works similarly to English build on:

• bygge på noe = build on something
• bygge videre på noe = continue building on something

So in this sentence, på innfallet tells you what she is building further on.

Here, videre is an adverb. It modifies the verb phrase bygger på.

It means something like:

• further
• on
• onward
• additionally

So it is not describing a noun; it is describing how she builds on the idea.

Bygger is the present tense of bygge.

• å bygge = to build
• bygger = builds / is building

In Norwegian, the present tense can often translate into English in more than one way depending on context:

• Hun bygger videre på innfallet.
  • She builds further on the idea.
  • She is building further on the idea.

This is a very normal Norwegian main-clause word order:

• Hun = subject
• bygger = verb
• videre på innfallet = the rest of the predicate

So the structure is basically:

Subject + verb + adverb/prepositional phrase

Nothing unusual is happening here. It is a standard declarative sentence.

Sometimes yes, but you should be careful.

Innfall can overlap with impulse, whim, or sudden idea, but in many contexts it is closer to:

• a sudden thought
• a flash of inspiration
• a notion that pops into your head

If you translate it as impulse, the English can sound more emotional or action-driven than the Norwegian sometimes does. In many cases, idea, notion, or whim may fit better.

Yes, you can, but the meaning changes slightly.

• Hun bygger på innfallet.
  = She builds on the idea.

• Hun bygger videre på innfallet.
  = She continues developing the idea / builds further on it.

So videre adds a sense of progression or continuation.

No. Very often it is used figuratively.

Literal:

• De bygger videre på huset.
  • They continue building on the house.

Figurative:

• Hun bygger videre på innfallet.
  • She develops the idea further.

In your sentence, it is clearly figurative: she is not physically constructing something, but expanding a thought or idea.