Mangelen gjelder forbrukerkjøpet.

Because -en marks the definite singular for many nouns in Bokmål.

• mangel = a defect / defect
• mangelen = the defect

So the sentence is talking about a specific defect, not defects in general.

The dictionary form is å gjelde.
Gjelder is the present tense form.

Depending on context, å gjelde can mean:

• to concern
• to apply to
• to be valid for

In formal or legal Norwegian, this verb is very common.

Because å gjelde often takes a direct object in Norwegian.

So:

• Mangelen gjelder forbrukerkjøpet

works like:

• The defect concerns the consumer purchase

In English, we often say applies to, but Norwegian very often just uses gjelder + noun directly.

Because Norwegian normally writes compound nouns as one word.

Here, the word is built from:

• forbruker = consumer
• kjøp = purchase

Together they form:

• forbrukerkjøp = consumer purchase

Then the definite ending is added:

• forbrukerkjøpet = the consumer purchase

Because the main noun in the compound is kjøp, and kjøp is a neuter noun.

Neuter nouns typically take -et in the definite singular:

• et kjøp = a purchase
• kjøpet = the purchase

The same pattern applies to the compound:

• et forbrukerkjøp = a consumer purchase
• forbrukerkjøpet = the consumer purchase

Because Norwegian usually shows definiteness with an ending on the noun instead of a separate article.

So:

• mangel → mangelen
• forbrukerkjøp → forbrukerkjøpet

That means the sentence already contains the twice, but it is built into the nouns.

In a normal Norwegian main clause, the basic order is:

• subject + verb + object

So here:

• Mangelen = subject
• gjelder = verb
• forbrukerkjøpet = object

Norwegian nouns usually do not show case endings, so word order is very important.

No. Kjøp is the general word for purchase.
Forbrukerkjøp is more specific and often has a legal meaning: it refers to a purchase made by a consumer, especially in contexts involving consumer rights and consumer sales law.

So this sentence sounds like it comes from a legal or official context, not casual conversation.

Yes. It is natural Norwegian, but it sounds clearly formal and somewhat legal/administrative.

That is mainly because of words like:

• mangel
• gjelder
• forbrukerkjøp

In everyday speech, people might use simpler wording, depending on the situation.

Not freely. Norwegian main clauses follow the V2 rule, which means the finite verb normally stays in second position.

The neutral word order here is:

• Mangelen gjelder forbrukerkjøpet

You can change the order in some contexts for emphasis, but then the verb still has to stay second. So for a learner, the original sentence is the safest and most natural pattern to remember.