Ako ima puno prašine, suha krpa nije dovoljna i moramo čistiti pažljivije.

In Croatian, ima can be used impersonally to mean there is / there are.

So:

• Ima puno prašine. = There is a lot of dust.

It does not mean someone literally has dust here.
This is a very common use of imati in everyday Croatian.

So Ako ima puno prašine means:

• If there is a lot of dust

not

• If someone has a lot of dust

Because after quantity words like puno (a lot of), Croatian usually uses the genitive.

Here:

• prašina = dust
• prašine = genitive form

So:

• puno prašine = a lot of dust

This is especially common with mass nouns like dust, water, sugar, sand, etc.

Compare:

• puno vode = a lot of water
• puno šećera = a lot of sugar
• puno prašine = a lot of dust

Because suha is an adjective and it must agree with the noun krpa in:

• gender
• number
• case

Here:

• krpa = cloth, rag
• it is feminine singular
• so the adjective must also be feminine singular

That gives:

• suha krpa = a dry cloth

Compare:

• suh stol = a dry table (masculine)
• suha krpa = a dry cloth (feminine)
• suho mjesto = a dry place (neuter)

Because dovoljna describes krpa, and adjectives in Croatian must agree with the noun they describe.

Since krpa is feminine singular, we get:

• suha krpa nije dovoljna = a dry cloth is not enough

Here dovoljna is an adjective meaning sufficient / enough.

By contrast, dovoljno is often used as:

• an adverb: radi dovoljno = he/she works enough
• a more neutral enough expression: To nije dovoljno. = That is not enough.

So in this sentence, because we are talking about the cloth, dovoljna is the correct form.

Because Croatian often drops subject pronouns when the verb ending already shows who the subject is.

• moramo = we must

The ending -mo tells you the subject is we, so mi is usually unnecessary.

You could say:

• mi moramo čistiti

but it is usually added only for emphasis or contrast, such as:

• Oni ne moraju, ali mi moramo.
  They don’t have to, but we do.

After the modal verb morati (must / have to), Croatian normally uses the infinitive.

So:

• moramo čistiti = we have to clean

Here:

• moramo = we must
• čistiti = to clean

The verb čistiti is the imperfective form, which fits well here because it refers to the activity in a general way: clean more carefully, not one single completed act.

Because pažljivije is an adverb, not an adjective.

It comes from:

• pažljivo = carefully
• pažljivije = more carefully

It describes how we must clean:

• moramo čistiti pažljivije = we must clean more carefully

If it were an adjective describing a noun, then you would see forms like:

• pažljiviji čovjek = a more careful man
• pažljivija žena = a more careful woman

But here it modifies the verb čistiti, so the adverb form pažljivije is needed.

It is the comparative form of the adverb pažljivo.

Pattern:

• pažljivo = carefully
• pažljivije = more carefully

So the sentence means that when there is a lot of dust, normal cleaning is not enough and we need to do it more carefully.

This comparative adverb works much like English more carefully, even though Croatian often forms it as a single word.

Because the sentence begins with a subordinate clause introduced by Ako (if).

Structure:

• Ako ima puno prašine, = If there is a lot of dust,
• suha krpa nije dovoljna... = a dry cloth is not enough...

Croatian normally uses a comma to separate this kind of if-clause from the main clause.

Not completely. Croatian word order is fairly flexible, but the version you have is a natural, neutral one.

Standard order here:

• Ako ima puno prašine, suha krpa nije dovoljna i moramo čistiti pažljivije.

You might also hear variations for emphasis, but learners should treat the given order as the safest normal pattern.

For example, moving words around may change emphasis:

• Ako ima puno prašine, nije dovoljna suha krpa...

This is still understandable, but it sounds more marked.
The original sentence is the best one to copy as a model.

Puno means a lot of / much / many, depending on context.

In this sentence:

• puno prašine = a lot of dust

Because dust is an uncountable idea, the best English translation is usually:

• a lot of dust
• or much dust (less natural in everyday English)

So puno is a very common quantity word, and it often triggers the genitive in the noun that follows.

Yes. In many situations, puno and mnogo can both mean a lot of.

So both are possible:

• puno prašine
• mnogo prašine

In everyday speech, puno is extremely common and often sounds a bit more conversational.

I means and.

Here it connects two main ideas:

• suha krpa nije dovoljna
• moramo čistiti pažljivije

So the logic is:

• If there is a lot of dust, a dry cloth is not enough, and we must clean more carefully.

It links the two consequences smoothly.

Because the sentence is talking about a dry cloth as a method or tool in a general sense.

• suha krpa nije dovoljna = a dry cloth is not enough

Croatian often uses the singular this way, just like English can:

• A dry cloth is not enough.

It does not necessarily mean only one specific cloth; it means the method using a dry cloth is insufficient.

It can be transitive, but in this sentence the object is simply not stated because it is understood from context.

• čistiti = to clean

In real use, Croatian often leaves out the object if it is obvious:

• Moramo čistiti pažljivije. = We have to clean more carefully.

The listener understands that we mean the surface, room, furniture, or whatever is being discussed.

So the sentence is perfectly natural even without saying exactly what we are cleaning.

Normally ako means if.

So here:

• Ako ima puno prašine... = If there is a lot of dust...

If you wanted when, Croatian would usually use kad or kada instead:

• Kad ima puno prašine... = When there is a lot of dust...

The difference is similar to English:

• if = condition
• when = time/situation expected to occur

In your sentence, ako is the normal choice because it presents a condition.