Learn Hardcore Danish: Hvis du mister dit pas i lufthavnen, bliver du meget nervøs. - If you lose your passport at the airport, you become very nervous.

miste → mister (present tense)
Used when you no longer have something, often because it has disappeared or gone out of your control.
tabe → taber (present tense)
Used for dropping something or losing a game/competition.

So you say:

Jeg mister mit pas. – I lose my passport (I can’t find it anymore).
Jeg taber mit pas på gulvet. – I drop my passport on the floor.
Vi taber kampen. – We lose the match.

With a passport, the natural expression is at miste sit/dit pas, because the idea is “it’s gone / you can’t find it,” not just “you dropped it.”

Why is it dit pas and not din pas?

The possessive pronouns din / dit / dine must agree with the grammatical gender and number of the noun:

din – with common gender (en-words), singular
- en bil → din bil (your car)
dit – with neuter gender (et-words), singular
- et pas → dit pas (your passport)
dine – with plural nouns, regardless of gender
- bøger → dine bøger (your books)

Pas is a neuter noun: et pas.
Therefore the correct form is dit pas, not din pas.

Why do we say i lufthavnen and not på lufthavnen?

The preposition i usually means in / inside and is used with many enclosed places and buildings:

i skolen – in/at the school
i banken – at the bank
i lufthavnen – at the airport (inside the airport area/buildings)

På (on, at) is used with many other locations, especially surfaces or some “open” places:

på gaden – in the street
på stationen – at the station
på arbejde – at work
på hospitalet – at (the) hospital

For lufthavn, the normal expression is i lufthavnen when you mean “at the airport” in the sense of being in that place / complex. You might occasionally hear på lufthavnen, but i lufthavnen is the standard and safest choice.

Why is it lufthavnen (the airport) instead of just lufthavn (airport)?

Danish normally marks definiteness by adding a suffix to the noun:

en lufthavn – an airport
lufthavnen – the airport

In your sentence, the context is specific: we’re talking about the particular airport you are in (or travelling from). English also uses the definite article here:

If you lose your passport at *the airport…*

If you wanted a more general statement, you could say:

Hvis du mister dit pas i en lufthavn, …
If you lose your passport in an airport, …

But in everyday speech, people very often imagine a concrete, specific airport situation, so i lufthavnen is natural.

Why is there a comma after lufthavnen?

Hvis du mister dit pas i lufthavnen is a subordinate clause (introduced by hvis = if).
bliver du meget nervøs is the main clause.

In written Danish, it is standard to put a comma between a subordinate clause and the main clause when they are next to each other:

Hvis du mister dit pas i lufthavnen, bliver du meget nervøs.

If you swap the order, you still put a comma between them:

Du bliver meget nervøs, hvis du mister dit pas i lufthavnen.

There are slightly different official comma systems, but for learners it is safe to remember:

Put a comma between the “hvis-clause” and the main clause.

Why is the word order bliver du instead of du bliver after the comma?

Danish main clauses follow a verb-second (V2) rule: the finite verb must come in second position in the sentence.

When the sentence starts with the hvis-clause, that entire clause counts as position 1. So the finite verb of the main clause, bliver, must come next (position 2), and the subject du comes after the verb:

Hvis du mister dit pas i lufthavnen, bliver du meget nervøs.
1. [Hvis-clause] – 2. bliver – 3. du – …

If you start with the subject instead, you don’t need inversion, because the subject itself is in position 1 and the verb naturally comes second:

Du bliver meget nervøs, hvis du mister dit pas i lufthavnen.
1. du – 2. bliver – 3. meget – …

So:

Fronted element (like a hvis-clause) → verb comes before the subject: bliver du
Normal order starting with subject → subject comes before the verb: du bliver

Why are mister and bliver in the present tense, even though this is about a future situation?

In Danish, it is very common to use the present tense to talk about a future event in if-clauses (and many other contexts), especially when the situation is general or typical:

Hvis du mister dit pas i lufthavnen, bliver du meget nervøs.
If you lose your passport at the airport, you (will) become very nervous.

This is similar to the English “zero conditional”:

If you lose your passport, you get very nervous.

You could say vil blive (will become) in Danish:

Hvis du mister dit pas i lufthavnen, vil du blive meget nervøs.

…but that sounds more formal and less natural in everyday speech here.
The simple present mister / bliver is the normal way to express a realistic or typical future consequence.

What is the difference between bliver du meget nervøs and er du meget nervøs?

blive = to become, to get → a change of state
være = to be → a state, not the change into it

In your sentence, you want to describe what happens when you lose your passport:

… bliver du meget nervøs.
… you become / get very nervous.

This shows the resulting change caused by losing the passport.

If you said:

Hvis du mister dit pas i lufthavnen, er du meget nervøs.

it would sound more like “If you lose your passport at the airport, (then) you are very nervous (in that situation).” It’s not wrong in all contexts, but bliver is much more natural here because it emphasizes the reaction or transition from calm → nervous.

Can we replace meget nervøs with something else, and does meget always go before the adjective?

Yes, you can use many other intensifiers instead of meget. Some common options:

virkelig nervøs – really nervous
rigtig nervøs – really/very nervous (colloquial)
helt vildt nervøs – extremely nervous (very informal)
meget, meget nervøs – very, very nervous

In Danish, adverbs of degree like meget, virkelig, helt, ret, rigtig normally come before the adjective:

meget nervøs – very nervous
virkelig træt – really tired
helt sikker – completely sure

You don’t say nervøs meget in this kind of structure.

How are hvis, mister, and lufthavnen pronounced, especially hv and the ending -en?

Very roughly (using English-like hints):

hvis – the h is silent. Sounds like “vis” (similar to English “vis” in “visible”, but shorter):
- Approximate: “vis”
mister – the -er ending is a weak, unstressed sound:
- Approximate: “MIS-ter”, but with a short first vowel (short i like in “sit”).
lufthavnen – three parts: luft
- havn
  - -en
    - luft – like English “looft” but with a shorter vowel
    - havn – roughly “hown” (like “town” but with h)
    - -en – weak, almost like “-un” / “-n”
    - Rough overall: “LUFT-hown-un”, with the stress on LUFT.

The exact Danish sounds are more complex than these approximations, but this will get you close enough for basic communication.