Saya menyimpan botol air di freezer, lalu menuang teh hangat dari teko ke dalam termos.

In Indonesian, if the subject stays the same, it is often left out in the second clause.

So:

Saya menyimpan botol air di freezer, lalu menuang teh hangat ...

naturally means:

I put the water bottle in the freezer, then I poured the warm tea ...

The second saya is understood automatically. You can say lalu saya menuang, but leaving it out sounds natural and less repetitive.

With verbs like menyimpan, menaruh, and meletakkan, Indonesian commonly uses di to show the place where something is put:

• menyimpan botol air di freezer
• menaruh buku di meja

Even though there is movement involved, the pattern is often verb + object + di + place.

By contrast, ke is more common with verbs that directly focus on movement toward a destination:

• pergi ke sekolah
• masuk ke rumah
• memasukkan botol air ke freezer

So in this sentence, di freezer is normal because the verb is menyimpan.

They are similar, but not exactly the same.

• menyimpan = to store, keep, put away
• menaruh / meletakkan = to put, place

In this sentence, menyimpan suggests putting the bottle in the freezer for a purpose, not just placing it somewhere casually.

So:

• Saya menyimpan botol air di freezer
  = I stored / put the water bottle in the freezer

If you used menaruh or meletakkan, it would focus more simply on the act of placing it there.

Both can be used.

• menuang = to pour
• menuangkan = to pour something out / to pour something into something

In everyday Indonesian, both of these can sound natural here:

• lalu menuang teh hangat dari teko ke dalam termos
• lalu menuangkan teh hangat dari teko ke dalam termos

Menuangkan can sound a little more explicit or slightly more formal, but menuang is very common and natural.

Lalu means then, after that, or next. It links actions in sequence.

Yes, kemudian can also be used:

• ..., lalu menuang teh hangat ...
• ..., kemudian menuang teh hangat ...

Both are correct. In general:

• lalu often sounds a bit more conversational and flowing
• kemudian can sound a bit more formal or written

Because the sentence shows both the starting point and the destination.

• dari teko = from the teapot
• ke dalam termos = into the thermos

So Indonesian is clearly marking:

1. where the tea comes from
2. where the tea goes

This is very natural with verbs like menuang.

Ke dalam emphasizes movement into the inside of something.

• ke termos = to the thermos
• ke dalam termos = into the thermos
• dalam termos = in the thermos

Because the tea is moving from one container to another, ke dalam termos is especially clear and natural.

You may hear ke termos in casual speech, but ke dalam termos is more precise.

• hangat = warm
• panas = hot

So teh hangat means warm tea, not hot tea.

This is an important vocabulary difference. If the tea were hotter, you would more likely say teh panas.

It can mean either, depending on context.

Indonesian noun combinations are often flexible, so botol air may refer to:

• a bottle used for water
• a bottle containing water

Usually the situation makes the meaning clear.

If you want to be more explicit, you could say:

• botol berisi air = a bottle containing water
• botol air minum = a drinking-water bottle / water bottle

Indonesian does not use articles the way English does.

So nouns like:

• botol air
• freezer
• teko
• termos

can mean a, the, or just the general idea of the noun, depending on context.

English requires you to choose between a bottle and the bottle, but Indonesian usually leaves that unstated unless it needs to be made clear.

In Indonesian, the main noun usually comes first.

• teh hangat = tea warm = warm tea
• botol air = bottle water = water bottle / bottle of water

So the usual pattern is:

• noun + adjective
• noun + noun modifier

That is why teh hangat sounds natural, while hangat teh does not.

Yes. They are very normal.

Indonesian uses many loanwords, especially for common objects and modern items.

• freezer is widely used
• termos is the Indonesian spelling of thermos

So even though they come from other languages originally, they are standard everyday vocabulary in Indonesian.