Bukselinningen sitter dårlig.

Because Norwegian very often forms compound nouns as a single word.

Here it breaks down like this:

• bukse = trousers / pants
• linning = waistband
• bukselinning = trouser waistband / pants waistband
• bukselinningen = the waistband

So what English often expresses with several words, Norwegian often packs into one noun.

In Norwegian, the is often attached to the end of the noun as a suffix.

So:

• en bukselinning = a waistband
• bukselinningen = the waistband

The ending -en is the definite ending here.

Because Norwegian uses bukse as a normal singular noun:

• en bukse = a pair of trousers / a pair of pants
• bukser = trousers / pants

So even though English usually uses a plural word, Norwegian does not have to. In compounds, Norwegian normally uses the base form, so bukse + linning becomes bukselinning.

Yes, literally sitter means sits, but in Norwegian it is also very commonly used for how clothes sit on the body.

So sitte godt or sitte dårlig often means:

• fit well / fit badly
• sit well / sit badly
• look right / look wrong on the body

This is very natural Norwegian. English often prefers fit, but Norwegian often prefers sitte in this kind of sentence.

Here dårlig means something like:

• badly
• not well
• poorly

In this sentence, it means the waistband does not sit right. Depending on context, that could mean it is:

• too tight
• too loose
• twisted
• uncomfortable
• generally not fitting properly

So it is about the fit or feel, not necessarily just one specific problem.

Not usually.

This sentence normally talks about how the waistband fits or sits, not about manufacturing quality.

So it suggests:

• the waistband does not sit properly
• the waistband feels wrong
• the waistband does not fit well

If you wanted to say it is badly made, you would usually say something more direct, such as Bukselinningen er dårlig laget.

Because dårlig here is describing how it sits, not directly describing the noun bukselinningen.

So in this sentence, dårlig works adverbially:

• sitter dårlig = sits badly / fits badly

Compare:

• en dårlig bukselinning = a bad waistband
  Here dårlig directly describes the noun.
• Bukselinningen sitter dårlig = The waistband fits badly
  Here dårlig describes the verb phrase.

That is why you do not use dårlige here.

Yes, you could, but the nuance is a little different.

• sitter dårlig focuses on how it sits on the body
• passer dårlig can mean it does not fit well or even does not suit well

For clothing, sitter dårlig often sounds more physical and natural when talking about the actual way the garment rests on someone. Passer dårlig is possible, but it can be broader and slightly less specific.

Because the speaker is being specific about which part is the problem.

• Buksen sitter dårlig = The trousers/pants fit badly
• Bukselinningen sitter dårlig = The waistband fits badly / sits badly

The second sentence does not necessarily mean the whole garment is wrong. It highlights the waistband as the problem area.

It follows the normal Norwegian pattern for a simple statement:

• Bukselinningen = subject
• sitter = verb
• dårlig = adverb/complement

So the structure is:

subject + verb + adverb

That is the standard word order in a main clause.

Some useful variations are:

• Bukselinningen sitter godt. = The waistband fits well.
• Bukselinningen sitter ikke godt. = The waistband does not fit well.
• Bukselinningen sitter for stramt. = The waistband is too tight.
• Bukselinningen sitter for løst. = The waistband is too loose.
• Bukselinningen sitter bedre nå. = The waistband fits better now.

These are very natural patterns to learn with sitte.

A rough learner-friendly guide would be:

• bukselinningen ≈ BUK-se-lin-ning-en
• sitter ≈ SIT-ter
• dårlig ≈ DOR-lig or DOAR-lig, depending on accent

A few helpful points:

• The main stress in bukselinningen is at the start: BUK-
• The tt in sitter is a short, crisp consonant
• The å in dårlig is not like English a in bad; it is a deeper vowel sound

Exact pronunciation varies somewhat by dialect, but those approximations will get you close.