Non sporcare il pavimento con il fango.

Because Non is the normal way to make a sentence negative in Italian.

• Sporcare il pavimento. = To dirty the floor.
• Non sporcare il pavimento. = Don’t dirty the floor.

In commands, non goes before the verb.

This is one of the most important points in the sentence.

With an informal singular negative command (when speaking to tu), Italian usually uses:

• non + infinitive

So:

• Sporca il pavimento. = Dirty the floor. / Make the floor dirty.
• Non sporcare il pavimento. = Don’t dirty the floor.

So even though the person being addressed is tu, the negative command uses the infinitive sporcare, not the imperative form sporca.

This sentence is addressing one person informally: tu.

Italian does not need to state the subject pronoun, so tu is understood.

So the full idea is:

• (Tu) non sporcare il pavimento con il fango.

That means Don’t dirty the floor with mud when speaking to one person you would normally address as tu.

The form changes depending on who you are speaking to:

• Non sporcare il pavimento con il fango. = informal singular (tu)
• Non sporcate il pavimento con il fango. = plural (voi)
• Non sporchi il pavimento con il fango. = formal singular (Lei)

So only the tu negative command uses the infinitive like this.

Sporcare means to make dirty, to dirty, or to soil.

It is a transitive verb, so it takes a direct object:

• sporcare il pavimento = to dirty the floor
• sporcare i vestiti = to dirty the clothes

Related words:

• sporco = dirty (adjective)
• sporcizia = dirt, filth
• sporcarsi = to get dirty / to make oneself dirty

In your sentence, sporcare means to make the floor dirty.

Because Italian normally uses an article before nouns in cases like this.

• il pavimento = the floor

Leaving out the article here would sound incomplete or unnatural in standard Italian.

So:

• sporcare il pavimento = to dirty the floor

This is very normal Italian structure: verb + article + noun.

Con il fango literally means with the mud or more naturally in English here, with mud.

• con = with
• il fango = the mud

In this sentence, it tells you what is causing the dirt:

• Non sporcare il pavimento con il fango.
• Don’t dirty the floor with mud.

Italian often uses the article where English may sound more natural without it, especially with substances and materials.

Italian frequently uses the definite article with general substances, materials, and abstract things in places where English may omit it.

So:

• con il fango is perfectly natural Italian
• in English, we usually just say with mud

You should not translate the article mechanically word for word. In many cases, Italian needs it even when English does not.

Yes, but the given order is the most neutral and natural.

Standard order here is:

• Non sporcare il pavimento con il fango.

This is:

• Non
  • verb + object + prepositional phrase

You may hear different word orders for emphasis, but this version is the straightforward one a learner should use first.

Here it is singular: il fango = the mud / mud.

Fango is often treated like a mass noun, similar to mud in English.

Plural exists:

• i fanghi

But in everyday speech, when talking about mud as a substance, the singular is much more common.

A simple pronunciation guide is:

Non sporcare il pavimento con il fango
non spor-KA-re il pa-vi-MEN-to con il FAN-go

A few notes:

• sporcare has stress on -ca-
• pavimento has stress on -men-
• fango has stress on fan-
• g in fango is a hard g, like in go

Yes, this sentence is completely natural.

Some alternatives you might also hear are:

• Non sporcare il pavimento di fango.
• Non infangare il pavimento.

But Non sporcare il pavimento con il fango is clear, correct, and easy for learners to understand.

The original sentence is a good standard example of a negative command.