Learn Hardcore Norwegian: Jeg jobber mer effektivt når huset er stille. - I work more efficiently when the house is quiet.

jobbe – more informal, everyday spoken Norwegian, very common.
arbeide – more formal or written style, used in official contexts, in writing, and in set expressions like arbeidsplass (workplace), arbeidstid (working hours).

In normal conversation, jobber is what you will hear most often. Both are correct here.

Why is it effektivt and not effektiv after jobber mer?

Effektiv is an adjective that describes a noun:

en effektiv metode – an efficient method
et effektivt system – an efficient system

When you want to describe how someone works (an adverb), Norwegian usually uses the neuter form of the adjective, which often ends in -t:

Jeg jobber effektivt. – I work efficiently.
Hun kjører forsiktig. – She drives carefully.
Han snakker klart. – He speaks clearly.

So effektivt here is functioning as an adverb: it describes the manner of working, not the worker or the work itself.

Why do we say mer effektivt and not effektivere?

Both patterns exist in Norwegian:

Comparative with -ere:
- rask → raskere (fast → faster)
- billig → billigere (cheap → cheaper)
Comparative with mer:
- interessant → mer interessant
- komfortabel → mer komfortabel

For most longer adjectives like effektiv, the normal and most natural comparative is with mer:

effektiv → mer effektiv / mer effektivt

You might see effektivere in some contexts, especially before a noun (for example, en mer effektiv / en effektivere metode), but as an adverb after a verb, mer effektivt is what sounds natural and idiomatic:

Jeg jobber mer effektivt is natural.
Jeg jobber effektivere sounds odd or at least unusual to native speakers.

Can I move mer effektivt to a different place in the sentence?

The standard word order is:

Jeg jobber mer effektivt når huset er stille.

Norwegian likes the finite verb (here jobber) in second position in main clauses. The usual and most neutral position for this kind of adverbial (manner) is after the verb and before the rest of the clause.

You could say, with a pause or for special emphasis:

Jeg jobber, når huset er stille, mer effektivt. (quite marked, spoken emphasis)

But most of these variants are either unnatural or sound wrong:

✗ Jeg mer effektivt jobber når huset er stille. – incorrect word order
✗ Jeg jobber når huset er stille mer effektivt. – sounds very awkward

So in practice, keep mer effektivt right after jobber here.

Why is the verb in the present tense jobber even though this seems like a general statement, not something happening right now?

Norwegian present tense covers both:

Something happening right now:
- Jeg jobber nå. – I am working now.
A habit, general truth, or regular situation (like English present simple):
- Jeg jobber mer effektivt når huset er stille. – I work more efficiently when the house is quiet.

So here, the sentence describes a general tendency or habit. English would use the simple present (I work more efficiently), and Norwegian also uses the simple present (jobber) for that.

Why is it når huset er stille and not da huset er stille?

Both når and da can translate to when, but they are used differently:

når
- General time, habits, repeated events, or future time:
  - Jeg jobber mer effektivt når huset er stille. – whenever the house is quiet
  - Når jeg kommer hjem, ringer jeg deg. – when I get home, I will call you.
da
- A single event in the past:
  - Jeg jobbet mer effektivt da huset var stille. – I worked more efficiently when the house was quiet (on that particular occasion or period)

In this sentence, we are talking about a general, repeated situation (whenever it is quiet), so når is the correct conjunction.

Why is the word order når huset er stille and not når er huset stille?

In Norwegian:

Main clauses (statements) have verb in second position:
- Huset er stille. – The house is quiet.
Yes/no questions invert:
- Er huset stille? – Is the house quiet?

But in subordinate clauses (introduced by når, at, fordi, etc.), the word order is normally:

conjunction – subject – verb – rest

So:

Når huset er stille – When the house is quiet

Using når er huset stille would be a question:

Når er huset stille? – When is the house quiet?

In your sentence, når huset er stille is not a question but a subordinate clause, so you must keep subject + verb there.

Why is it huset and not hus? Where is the word for the?

Norwegian usually attaches the definite article as a suffix to the noun:

hus – a house
huset – the house
bok – a book
boka / boken – the book

So huset literally means the house.

In your sentence:

når huset er stille
– when the house is quiet

There is no separate word like English the; it is built into huset.

Why is stille not stillt or something with a -t ending?

Adjectives in Norwegian change form, but not all of them add -t in neuter or adverbial use.

For many adjectives:

rask → raskt (neuter/adverb)
klar → klart

However, for adjectives ending in -e, -ig, -lig, -sk, you generally do not add an extra -t:

stille → stille
rolig → rolig
vanlig → vanlig

So:

Huset er stille. – The house is quiet.
Det er stille her. – It is quiet here.

There is no form stillt; that would be incorrect.

Could I say Jeg arbeider mer effektivt når huset er stille instead, and is there any nuance difference?

Yes, you can. Grammatically, it is fine:

Jeg arbeider mer effektivt når huset er stille.

The nuance:

jobber – sounds more everyday, neutral, spoken.
arbeider – sounds slightly more formal, literary, or official.

In normal conversation, jobber is more typical, but both versions communicate the same meaning.

Can I say Jeg jobber best når huset er stille instead of mer effektivt?

Yes, that is another very natural way to express a similar idea:

Jeg jobber best når huset er stille. – I work best when the house is quiet.

Nuance:

mer effektivt – focuses on being more efficient than usual, maybe compared to other situations.
best – says that this is your optimal or favorite working condition.

Both are idiomatic; which one you choose depends on what you want to emphasize.