Operasi itu berjalan lancar.

Not always. Operasi can mean:

• surgery / an operation in a medical context
• an operation in a military, police, business, or technical context

So the exact meaning depends on the situation. In Operasi itu berjalan lancar, operasi could be a medical procedure, a police operation, a military mission, and so on.

Itu usually means that, but after a noun it often works like the in English, making something specific or already known.

So:

• operasi = an operation
• operasi itu = that operation / the operation

In this sentence, itu points to a specific operation already understood from context.

In Indonesian, demonstratives like ini and itu normally come after the noun.

For example:

• rumah ini = this house
• rumah itu = that house
• operasi itu = that operation

This is one of the basic word-order differences from English.

Yes, berjalan literally can mean to walk. But it is also very commonly used figuratively to mean:

• to run
• to proceed
• to take place
• to go on

So in this sentence, berjalan does not mean the operation was physically walking. It means the operation proceeded or went in a certain way.

Lancar means smooth, without problems, without interruptions, or fluently, depending on context.

In this sentence, lancar means the operation went smoothly or without any trouble.

You may also see lancar in other contexts, such as:

• Bahasa Indonesianya lancar = His/Her Indonesian is fluent.
• Lalu lintas lancar = Traffic is flowing smoothly.

Indonesian does not usually change adjectives into adverbs the way English does with -ly.

So an adjective can often function like an adverb depending on position and context.

Here:

• berjalan lancar = to go smoothly

Even though lancar is basically an adjective, in this sentence it describes how the operation proceeded.

Indonesian does not mark tense the same way English does. Verbs usually do not change form for past, present, or future.

So berjalan can mean:

• goes
• is going
• went
• was going

The time is normally understood from context or from time words such as:

• kemarin = yesterday
• tadi = earlier
• besok = tomorrow

So Operasi itu berjalan lancar could mean The operation went smoothly or The operation is going smoothly, depending on context.

No. The main verb here is berjalan.

The structure is:

• Operasi itu = the operation
• berjalan = proceeded / went
• lancar = smoothly / smoothly-running

So this is not a sentence that needs a separate to be verb. Indonesian often omits a copula anyway, but in this case the sentence already has its main verb.

Yes. Operasinya berjalan lancar is also natural.

Here, -nya can make operasi definite, giving a meaning like:

• the operation
• his/her/their operation
• the operation in question

So:

• Operasi itu berjalan lancar
• Operasinya berjalan lancar

can both mean something like The operation went smoothly, though the nuance depends on context.

Yes, very common. It is a standard way to say that something is going well or proceeding smoothly.

You can use it for many things, for example:

• Acara itu berjalan lancar = The event went smoothly.
• Rapat berjalan lancar = The meeting went smoothly.
• Proyeknya berjalan lancar = The project is going smoothly.

So this pattern is very useful to learn.

Yes, you can, but it sounds a little different.

• Operasi itu berjalan lancar emphasizes that the operation proceeded smoothly.
• Operasi itu lancar is shorter and can sound like The operation was smooth / went fine.

The version with berjalan is especially natural when talking about how an event or process unfolded.

A simple pronunciation guide is:

oh-peh-RAH-see EE-too ber-JAH-lan LAHN-char

A few notes:

• r in Indonesian is usually rolled or tapped
• c is pronounced like ch in church
• stress is not as strong or dramatic as in English, but this guide helps approximate it

So lancar sounds like LAHN-char, not like English lan-kar.