Als je je instapkaart laat zien, kom je snel door de veiligheidscontrole.

The first je is the subject: you.

The second je means your and is a possessive determiner before instapkaart.

So:

• je = you
• je instapkaart = your boarding pass

Dutch often uses je for both you and your, so this kind of repetition is completely normal.

Because the sentence starts with als (if/when), the first part is a subordinate clause. In Dutch subordinate clauses, the verbs usually move toward the end.

So:

• main-clause order: subject + verb + rest
• subordinate-clause order: subject + rest + verb(s) at the end

Here:

• Als je je instapkaart laat zien
• literally: If you your boarding pass show-let

The verb group laat zien comes at the end of the als clause.

This is one of the most important Dutch word-order patterns to get used to.

Laten zien means to show.

Literally, laten often means to let, and zien means to see, but together laten zien is a fixed expression meaning show.

Examples:

• Kun je je paspoort laten zien? = Can you show your passport?
• Ik laat mijn ticket zien. = I show my ticket.

So in your sentence, je instapkaart laten zien means to show your boarding pass.

In Dutch, separable or multi-part verb combinations often place the parts together at the end of a subordinate clause.

In a main clause, you might see separation more clearly:

• Je laat je instapkaart zien.

Here laat is the finite verb and zien comes later.

In the subordinate clause:

• Als je je instapkaart laat zien

both verb parts end up together at the end.

So this is normal Dutch word order for this kind of verb phrase.

Because the sentence begins with the als clause:

• Als je je instapkaart laat zien, ...

That whole clause takes the first position in the sentence. In Dutch main clauses, the finite verb must come in the second position. So after the opening clause, the verb comes before the subject:

• ..., kom je snel door de veiligheidscontrole.

This is called inversion.

Compare:

• Je komt snel door de veiligheidscontrole. = You get through security quickly.
• Als je je instapkaart laat zien, kom je snel door de veiligheidscontrole.

Same meaning structure, just different word order because of what comes first.

Door ... komen means to get through ... or to pass through ....

So:

• door de veiligheidscontrole komen = to get through security / the security check

A few useful related examples:

• We kwamen snel door de douane. = We got through customs quickly.
• Hij kwam moeilijk door het examen. = He passed the exam with difficulty.
  (Different context, but door ... komen can also mean getting through or passing something.)

In your sentence, it refers to airport security.

Veiligheidscontrole is the more standard Dutch word for security check or security screening.

It is a compound noun:

• veiligheid = safety/security
• controle = check/inspection

So de veiligheidscontrole means the security check.

In real life, Dutch speakers may also use English-influenced words like security, especially in airport contexts, but veiligheidscontrole is clear, correct, and standard.

These nouns take the article de, not het:

• de instapkaart
• de veiligheidscontrole

Unfortunately, grammatical gender in Dutch often has to be learned noun by noun. There are some patterns, though:

• words ending in -kaart are usually de words
• many nouns ending in -ie, -tie, -teit, -heid, and often -controle-type abstract nouns are de words

So these two being de is not surprising.

Yes, depending on context.

Als can mean:

• if = under that condition
• when = whenever/in the situation that

In your sentence, English could interpret it as:

• If you show your boarding pass, you get through security quickly
• or When you show your boarding pass, you get through security quickly

Dutch als often covers both ideas. Context tells you whether it is a real condition or more of a general statement.

Dutch often uses the present tense for:

• general truths
• instructions
• scheduled events
• future situations that are clear from context

So:

• Als je je instapkaart laat zien, kom je snel door de veiligheidscontrole.

uses present tense, but it can refer to what will happen in that situation.

English does something similar:

• If you show your boarding pass, you get through quickly.
• When you arrive, you go to security.

So this is very natural Dutch.

Snel is an adverb meaning quickly. In Dutch, adverbs often come before prepositional phrases like door de veiligheidscontrole.

So:

• kom je snel door de veiligheidscontrole

sounds natural because snel modifies how you get through security.

You may also hear variations depending on emphasis, but this order is very normal and idiomatic.

Yes, but the nuance is a little different.

• je instapkaart laten zien = the most everyday, natural way to say show your boarding pass
• je instapkaart tonen = also correct, but often sounds a bit more formal or official

So both are possible:

• Als je je instapkaart laat zien, kom je snel door de veiligheidscontrole.
• Als je je instapkaart toont, kom je snel door de veiligheidscontrole.

For normal conversation, laten zien is often the more common choice.

No. Dutch speakers may use different terms, including:

• instapkaart
• boardingpass / boarding pass
• sometimes boardingkaart, though this is less standard

Instapkaart is a good, clear Dutch word:

• instappen = to board
• kaart = card/ticket

So it literally means something like boarding card.

At airports, English loanwords are also very common, but instapkaart is perfectly good Dutch.

Yes. When a subordinate clause comes before the main clause, Dutch normally separates them with a comma.

So:

• Als je je instapkaart laat zien, kom je snel door de veiligheidscontrole.

That comma helps mark the boundary between:

1. the als clause
2. the main clause

This is standard punctuation in Dutch.