Sikkerhedskontrollen ligger før paskontrollen.

Because Danish usually adds the definite article to the end of the noun.

• en kontrol = a check / a control
• kontrollen = the check / the control

So:

• sikkerhedskontrol = security check
• sikkerhedskontrollen = the security check
• paskontrol = passport control
• paskontrollen = the passport control

This is very normal in Danish. Instead of a separate word like English the, Danish often uses a suffix such as -en, -et, or -ne.

It can literally mean lies, but in sentences like this it usually means is located or is situated.

So Sikkerhedskontrollen ligger før paskontrollen is not saying the security check is physically lying down. It means:

• The security check is located before the passport control
• The security check comes before passport control

Danish often uses ligge for places, buildings, rooms, and areas:

• Toilettet ligger derovre. = The toilet is over there / is located over there.
• Hotellet ligger tæt på stationen. = The hotel is near the station.

Because før means before in the sense of earlier than or coming prior to.

In this airport sentence, før is the natural choice because it describes the order you meet things in.

• før = before
• foran = in front of

So:

• Sikkerhedskontrollen ligger før paskontrollen = The security check comes before passport control
• Sikkerhedskontrollen ligger foran paskontrollen would suggest a more physical in front of relationship, which is usually not the best way to describe this kind of sequence.

Yes. It follows standard main-clause word order:

• Sikkerhedskontrollen = subject
• ligger = verb
• før paskontrollen = adverbial phrase

Danish is a V2 language, which means the finite verb usually comes in the second position in a main clause.

So this sentence is completely normal:

• Sikkerhedskontrollen ligger før paskontrollen.

If you move another element to the front, the verb still stays second:

• Før paskontrollen ligger sikkerhedskontrollen.

That version is grammatical, but less natural in most situations.

Because Danish, like German, often forms compound nouns by writing them as a single word.

So:

• sikkerhed = security
• kontrol = check/control
• sikkerhedskontrol = security check

And:

• pas = passport
• kontrol = control/check
• paskontrol = passport control

This is very common in Danish. English often writes these as two words, but Danish usually combines them into one.

You might be understood, but ligger is much more natural.

Danish often prefers ligger when talking about where something is located in a building, route, or space.

• ligger = is situated / is located
• er = is

Using er here sounds less idiomatic. Native speakers are more likely to say:

• Sikkerhedskontrollen ligger før paskontrollen.

A rough pronunciation guide is:

SIK-er-heths-kon-TROL-en LIG-er føhr PAS-kon-TROL-en

A few helpful notes:

• sikkerhed has a soft d at the end, which is often not pronounced like a strong English d
• ligger sounds roughly like LIG-er
• før has the Danish vowel ø, which does not exist exactly in English; it is somewhat like the vowel in French peur or German schön, depending on accent
• kontrollen has the stress on the last main part: -trol-

If you want a more natural rhythm, try saying it in chunks:

Sikkerhedskontrollen | ligger før | paskontrollen

No. In modern Danish, nouns are not capitalized unless they begin the sentence or are part of a proper name.

So in this sentence:

• Sikkerhedskontrollen is capitalized only because it is the first word.
• paskontrollen stays lowercase.

This is different from German, where all nouns are capitalized.

Yes. kontrol is a common gender noun in Danish, so it takes en in the indefinite singular:

• en kontrol
• kontrollen

That is why both compounds also take -en in the definite singular:

• sikkerhedskontrollen
• paskontrollen

If the head noun were a neuter noun, the definite ending would usually be -et instead.