pasokon no kiiboodo ni mizu wo kobosanai you ni ki wo tukete imasu.

A natural way to parse it is:

• パソコンのキーボードに = onto/on the computer keyboard
• 水をこぼさないように = so as not to spill water
• 気をつけています = I am being careful / I make sure

So the grammar flow is basically:

[place affected] に + [thing] を + [negative verb] ように + 気をつけている

That makes it easier to see how the sentence is built.

の connects two nouns. Here it shows the relationship between パソコン and キーボード:

• パソコン = computer
• キーボード = keyboard
• パソコンのキーボード = the computer’s keyboard / the keyboard of the computer

This is very common in Japanese. A の B often means:

• B of A
• A’s B
• B related to A

So this is just the normal way to say computer keyboard.

Here, に marks the place or target that would receive the spilled water.

So:

• キーボードに水をこぼす = to spill water onto the keyboard

This に is not marking direction in the same way as go to somewhere. It marks the surface or destination of the spilling.

Compare:

• 床に水をこぼす = spill water on the floor
• 服にコーヒーをこぼす = spill coffee on clothes
• キーボードに水をこぼす = spill water on the keyboard

This is about the transitive/intransitive pair:

• こぼす = to spill something
• こぼれる = something spills / something gets spilled

So:

• 水をこぼす = spill water
• 水がこぼれる = water spills

In this sentence, the speaker is talking about their own action and trying not to do it, so こぼす is the right verb.

That is why the sentence uses:

• 水をこぼさない = not spill water

rather than:

• 水がこぼれない = water does not spill

Both can be grammatical in different contexts, but this sentence focuses on preventing yourself from spilling it.

こぼさない is the plain negative form of こぼす.

Conjugation:

• dictionary form: こぼす
• negative: こぼさない

So:

• 水をこぼす = spill water
• 水をこぼさない = not spill water

This negative form is used before ように in a very common pattern:

• Vないように = so as not to do V

〜ないように means so as not to..., in order not to..., or to make sure not to...

In this sentence:

• 水をこぼさないように = so as not to spill water

This pattern is extremely common when talking about caution, effort, or prevention.

Examples:

• 忘れないようにメモします。
  I write a note so I won’t forget.

• 風邪をひかないように気をつけてください。
  Please be careful not to catch a cold.

So here the speaker is saying they are careful with the goal of avoiding spilling water.

They are doing completely different jobs.

1. キーボードに
   This に marks the place/target of the spilling:
   onto the keyboard

2. こぼさないように
   This に is part of the grammar pattern ように, which means
   so that / so as to

So even though they look the same, they are not the same kind of に.

気をつける means to be careful, to pay attention, or to take care.

So:

• 気をつけています = I am being careful / I’m taking care

In this sentence, it means the speaker is consciously paying attention to avoid spilling water on the keyboard.

It is a very common expression:

• 気をつけてください。 = Please be careful.
• 健康に気をつけています。 = I take care of my health.
• 遅れないように気をつけています。 = I make sure not to be late.

〜ている often shows an ongoing state or habitual action.

So:

• 気をつけます can sound like I will be careful or I am careful in a more simple/polite statement.
• 気をつけています suggests I am currently keeping this caution in mind or I habitually make sure to be careful.

In this sentence, 気をつけています feels natural because being careful is an ongoing state, not a one-time action.

So the nuance is something like:

• I’m being careful
• I keep being careful
• I make a point of being careful

Yes, very common.

The pattern:

• Vないように気をつける = be careful not to do V
• Vように気をつける = be careful to do V

Examples:

• 間違えないように気をつけます。
  I’ll be careful not to make mistakes.

• 毎日運動するように気をつけています。
  I try to make sure I exercise every day.

So 水をこぼさないように気をつけています is a very standard and natural structure.

Yes, but the nuance changes a little.

• 水をこぼさないように気をつけています
  = I’m being careful not to spill water.

• 水をこぼさないようにしています
  = I try not to spill water / I make a point of not spilling water.

気をつけています emphasizes caution/attention.
ようにしています emphasizes making it a habit or effort.

Both are natural, but 気をつけています fits especially well when talking about avoiding an accident.

Because ように already forms the adverbial phrase that connects to 気をつける.

So this part:

• こぼさないように

acts like:

• so as not to spill

and it directly modifies 気をつけています.

You do not need another particle there.
The structure is already complete.

Normally, に is the natural choice here.

• キーボードに水をこぼす = spill water onto the keyboard

Using で would not sound right for the target of the spill in this sentence.

That is because で usually marks:

• the place where an action happens
• the means/tool used
• a cause, etc.

But here the keyboard is not the location where the spilling action is performed in a general sense; it is the surface affected by the spill, so に is the normal particle.

Yes, it is natural.

A native speaker might also say things like:

• パソコンのキーボードに水をこぼさないように気をつけています。
• パソコンのキーボードに飲み物をこぼさないように気をつけています。
• キーボードに水をこぼさないように注意しています。

Your sentence sounds perfectly normal for everyday Japanese.

In normal Japanese writing, there would usually be no spaces:

• パソコンのキーボードに水をこぼさないように気をつけています。

The spaces in your version are just for learning purposes, to make the parts easier to see. Japanese is normally written without spaces between words.

パソコン is a general word for personal computer and can refer to a desktop or laptop depending on context.

So パソコンのキーボード could mean:

• the keyboard of a desktop computer
• the keyboard of a laptop

If the speaker specifically wanted to make it clear that it was a laptop keyboard, they might use ノートパソコン. But as written, パソコン is broad and natural.

A very useful pattern to remember is:

• N に O を Vないように 気をつけている
• be careful not to V O onto/at N

More generally:

• Vないように気をつける = be careful not to do V

Examples:

• 転ばないように気をつけてください。
  Please be careful not to fall.

• 塩を入れすぎないように気をつけています。
  I’m careful not to add too much salt.

• スマホを落とさないように気をつけています。
  I’m careful not to drop my phone.

If you remember Vないように気をつける, this sentence becomes much easier to understand.