Setelah pesawat mendarat, kami berjalan ke bagian imigrasi dengan tenang.

Setelah means after.

In this sentence, setelah pesawat mendarat means after the plane landed or more literally after the plane lands/has landed.

A useful pattern is:

setelah + clause

For example:

• Setelah saya makan, saya tidur. = After I ate, I slept.
• Setelah dia datang, kami mulai. = After he arrived, we started.

In your sentence, the clause pesawat mendarat comes after setelah, and then the main clause follows:

• Setelah pesawat mendarat, kami berjalan ...

This is very natural in Indonesian.

Indonesian does not usually use articles like the or a/an.

So:

• pesawat can mean plane, a plane, or the plane
• bagian imigrasi can mean the immigration section/area

The exact meaning is understood from context.

That is why pesawat mendarat can naturally mean the plane landed without needing a separate word for the.

Mendarat means to land.

So:

• pesawat mendarat = the plane lands / landed

The base word is darat, which relates to land (as opposed to sea or air). With the meN- prefix, it becomes the verb mendarat, meaning to land.

You do not need to translate the parts literally every time, but it helps to know that Indonesian often builds verbs this way.

Examples:

• Pesawat itu mendarat pukul 8. = The plane landed at 8.
• Burung itu mendarat di atap. = The bird landed on the roof.

This is a very common question, because English only has we, but Indonesian has two common forms:

• kami = we, but not including the person being spoken to
• kita = we, including the person being spoken to

So in this sentence:

• kami berjalan = we walked, but the listener is not part of that group

If the speaker were including the listener, kita would be used instead.

Examples:

• Kami sudah makan. = We already ate. (not including you)
• Kita sudah makan. = We already ate. (including you)

Yes, berjalan literally means to walk.

So:

• kami berjalan ke bagian imigrasi = we walked to the immigration area

The root is jalan = road, way, walk, go on foot in some contexts.
With ber-, berjalan becomes an intransitive verb meaning to walk.

It can also sometimes mean to run/function/proceed, depending on context:

• Mesinnya berjalan dengan baik. = The machine is running well.
• Pertemuan berjalan lancar. = The meeting went smoothly.

But in your sentence, because it is followed by ke bagian imigrasi, the meaning is clearly physical walking.

Yes, but the meaning would change slightly.

• berjalan = to walk
• pergi = to go

So:

• kami berjalan ke bagian imigrasi emphasizes that they went there on foot
• kami pergi ke bagian imigrasi just means we went to the immigration area, without focusing on how

Because people normally go to immigration by walking after landing, berjalan sounds natural and specific.

Ke means to, toward, or into a place/direction.

So:

• ke bagian imigrasi = to the immigration section/area

It is a preposition used for movement toward a place.

Examples:

• Saya pergi ke hotel. = I went to the hotel.
• Mereka lari ke luar. = They ran outside.

Do not confuse ke with di:

• ke = to
• di = at / in / on

So:

• Kami berjalan ke bagian imigrasi. = We walked to immigration.
• Kami berada di bagian imigrasi. = We were at the immigration section.

Literally, bagian means part, section, or department.

So bagian imigrasi literally means something like:

• the immigration section
• the immigration area
• the immigration department

In an airport context, it refers naturally to the immigration area or checkpoint.

Indonesian often uses noun + noun combinations like this, where the second noun describes the first:

• bagian imigrasi = immigration section
• kantor polisi = police office / police station
• meja makan = dining table

Dengan tenang means calmly or in a calm manner.

• dengan = with
• tenang = calm

So literally it is with calmness/calmly.

Indonesian often expresses adverbial meanings this way:

• dengan cepat = quickly
• dengan hati-hati = carefully
• dengan tenang = calmly

English often uses -ly, but Indonesian frequently uses dengan + adjective/adverbial expression.

In this sentence, dengan tenang describes how kami berjalan.

Because it modifies the verb phrase kami berjalan ke bagian imigrasi and tells us how the action was done.

Putting it at the end is very natural in Indonesian:

• Kami berjalan ke bagian imigrasi dengan tenang.

This is similar to English:

• We walked to immigration calmly.

Indonesian word order is often flexible, but the end position is common and natural for adverbial phrases like this.

You may also hear variations depending on emphasis, but the original sentence is the most neutral and natural.

Indonesian verbs do not change form for tense the way English verbs do.

So:

• mendarat can mean land / lands / landed
• berjalan can mean walk / walked

Time is usually understood from:

1. context
2. time words
3. sequence of events

In this sentence, setelah already shows the sequence:

• first, the plane landed
• then, we walked to immigration

Because the whole situation is clearly a completed travel event, English naturally translates it in the past:

• After the plane landed, we walked to immigration calmly.

If Indonesian needs to be more explicit, it can add words like:

• sudah = already
• tadi = earlier
• kemarin = yesterday

For example:

• Setelah pesawat sudah mendarat, kami berjalan ke bagian imigrasi.

The comma is appropriate and natural here because the sentence begins with a subordinate clause:

• Setelah pesawat mendarat, ...

That introductory clause is followed by the main clause:

• kami berjalan ke bagian imigrasi dengan tenang.

In writing, the comma helps readability, just like in English:

• After the plane landed, we walked to immigration calmly.

In casual writing, some people may omit commas, but using one here is correct and clear.

It can, depending on context, because Indonesian does not mark tense the same way English does. However, in this sentence, the most natural interpretation is the plane landed.

That is because setelah usually introduces an event that is completed before the next event:

• first: pesawat mendarat
• then: kami berjalan ke bagian imigrasi

So in context, after the plane landed is the best translation.

If someone wanted to emphasize an ongoing action like was landing, they would usually need a different context or extra wording.