Luggen er for lang, så jeg må klippe den.

Luggen refers to the hair at the front of the head that falls over the forehead.

• In British English, this is usually the fringe
• In American English, this is usually the bangs

So it does not mean all of the hair, just that front part.

Because luggen is the definite singular form.

• en lugg = a fringe / a bang section
• luggen = the fringe / the bangs

Norwegian often uses the definite form when talking about a specific, known thing, and here the speaker means their own fringe/bangs.

This is just a difference between the languages.

In English, bangs is usually plural. In Norwegian, lugg is normally treated as a singular noun. That is why the rest of the sentence also uses singular grammar:

• luggen = singular
• lang = singular adjective form here
• den = singular pronoun

So even if the English meaning is plural-looking, the Norwegian grammar is singular.

Because the adjective has to match the noun grammatically.

Here, luggen is:

• singular
• common gender

So the predicate adjective is lang:

• en lugg er lang
• et hår er langt
• hårene er lange

That is why lang is correct in this sentence.

Because lang describes physical length, while lenge is about time.

• lang = long in size/length
• lenge = for a long time

Here the sentence is talking about hair being too long physically, so lang is the right word.

Here for means too, in the sense of excessively.

So for lang means too long.

This is a very common pattern in Norwegian:

• for dyr = too expensive
• for varm = too warm
• for sent = too late

This for is not the English-style for meaning for someone/something.

Here så means so or therefore.

It links the two ideas:

• Luggen er for lang = the fringe/bangs is too long
• så jeg må klippe den = so I have to cut it

So it shows a result or consequence.

Because in this sentence så is functioning as a coordinating conjunction meaning so, joining two main clauses.

After that kind of så, Norwegian keeps normal main-clause order:

• så jeg må klippe den

not inversion.

Compare that with a word like derfor:

• Luggen er for lang. Derfor må jeg klippe den.

After derfor, you do get inversion: må jeg.

So this is a useful contrast:

• så jeg må ...
• derfor må jeg ...

Må is the present tense of måtte and usually means:

• must
• have to
• need to

In a sentence like this, it often sounds like practical necessity rather than a dramatic obligation. The idea is basically: the fringe/bangs is too long, so cutting it is necessary.

Because må is a modal verb, and after modal verbs Norwegian normally uses the bare infinitive.

So you get:

• jeg må klippe
• jeg kan klippe
• jeg vil klippe
• jeg skal klippe

not jeg må å klippe.

The form å klippe is used when the infinitive stands on its own or after other kinds of verbs and expressions.

Because den refers back to luggen, and lugg is a common-gender singular noun.

In Norwegian:

• den = common-gender singular
• det = neuter singular
• de/dem = plural

So:

• luggen ... den = correct

Even though English often says bangs, Norwegian treats lugg as singular, so den is the right pronoun.

Yes. Klippe is the most natural verb here.

For hair, Norwegian typically says:

• klippe håret
• klippe luggen

A verb like kutte can mean cut in a general sense, but for hair klippe is the standard and most idiomatic choice.