Air tumpah di lantai, jadi saya mengambil lap.

This is a very common false friend.

In Indonesian, air means water.
The English word air is usually udara in Indonesian.

So:

• air = water
• udara = air

A useful extra note: Indonesian air is pronounced roughly ah-eer (two syllables), not like the English word air.

Indonesian does not use articles the way English does.

So bare nouns like air, lantai, and lap can often mean:

• water / the water / some water
• floor / the floor
• a rag / the rag

The exact meaning depends on context.

That is why Air tumpah di lantai can naturally mean something like Water spilled on the floor or The water spilled onto the floor, depending on the situation.

Because tumpah is used when something spills / is spilled, without focusing on a person doing the action.

In this sentence, the water is the thing that spilled:

• Air tumpah = The water spilled / The water is spilled

If you want to say that someone actively spilled something, you would use a transitive form such as menumpahkan:

• Saya menumpahkan air. = I spilled the water.

So the difference is roughly:

• tumpah = spill, be spilled
• menumpahkan = spill something

It behaves like a predicate, and English learners often feel it is somewhere between a verb and an adjective.

In Indonesian, many roots can work in ways that do not match English categories perfectly. In Air tumpah, tumpah expresses the state/event of the water having spilled.

So in English you might translate it as:

• The water spilled
  or
• The water is spilled

There is no need for a word like is in Indonesian here.

Yes, here di marks location, and in English that may become in, on, or at depending on the noun.

So:

• di lantai = on the floor
• di rumah = at home
• di kotak = in the box

Indonesian di is a general location marker. English is more specific, so the translation changes.

Also, note that di as a preposition is written separately:

• di lantai ✔
• dilantai ✘

Here jadi means so, therefore, or as a result.

It links the two ideas:

• water spilled on the floor
• as a result, I got a rag

So it works much like English so in:

• The water spilled, so I got a rag.

Be aware that jadi can have other meanings in other contexts, such as become, but in this sentence it is a connector meaning so.

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

So mengambil can mean:

• take
• takes
• took
• will take

Context tells you the time.

In this sentence, the sequence of events makes it clear that it is past in meaning:

• water spilled
• so I got a rag

If you wanted to make the past meaning more explicit, you could add a time word such as tadi or sudah, depending on context.

Yes. Here mengambil means something like get, grab, or take.

So mengambil lap means get a rag / grab a wiping cloth.

In English, take can sound a little odd by itself, but in Indonesian mengambil is very natural for going to get something you need.

Depending on context, English might translate it more naturally as:

• I got a rag
• I grabbed a cloth
• I went to get a rag

Yes, lap can be understood as a wiping cloth/rag, and it is also related to the verb to wipe.

In this sentence, after mengambil, it is understood as a noun:

• lap = rag / wiping cloth

A more explicit form is:

• kain lap = wiping cloth / rag

If you wanted lap as a verb, the sentence structure would look different, for example:

• Saya lap lantainya. = I wiped the floor.

So in mengambil lap, the context makes lap a noun.

Saya is the more neutral and polite word for I.
Aku is more informal and personal.

So:

• saya = neutral, polite, common in standard Indonesian
• aku = informal, casual, often used with friends, family, or in a more intimate tone

In a textbook-style sentence, saya is very common.

You could say:

• Air tumpah di lantai, jadi aku mengambil lap.

That is still understandable, but it sounds more casual.

Yes, it is understandable and basically natural.

A few common variations are:

• Air tumpah di lantai, jadi saya mengambil kain lap.
  Slightly clearer because kain lap explicitly means wiping cloth.

• Air tumpah di lantai, jadi saya ambil lap.
  More casual spoken style; ambil is very common in everyday speech.

• Ada air tumpah di lantai, jadi saya mengambil lap.
  This can sound like There was spilled water on the floor, so I got a rag.

So the original sentence is fine, but native speakers may choose slightly different wording depending on formality and context.