Ti prego, non versare l’acqua: il tavolo è già un po’ bagnato.

In Italian, the negative imperative for tu (the informal “you”) is made by placing non before the infinitive. So instead of saying versa for “pour” (positive command), you say non versare for “don’t pour.” Positive:

• (tu) Versa l’acqua!
  Negative:
• (tu) Non versare l’acqua!

Italian drops the vowel of the definite article la before another word that starts with a vowel. The apostrophe signals that the a has been omitted:

• la + acqua → l’acqua

Un po’ is a shortened form of un poco (a little). The apostrophe replaces the omitted co, so you write po’ instead of poco when you want a concise, colloquial feel:

• il tavolo è già un po’ bagnato = the table is already a bit wet

Già means “already.” In Italian it generally comes directly before the adjective or adverb it modifies. Here it emphasizes that the table is “by now a little wet,” so you say:

• il tavolo è già un po’ bagnato

In English you might say “the table got wet,” but in Italian the past participle bagnato functions as an adjective describing the table’s state. You use essere to link the subject with that adjective:

• Il tavolo è bagnato.

Yes. Versare is the most common for “pour” or “spill (liquid).” Other options include:

• rovesciare (more like “knock over” or “upend” and spill all at once)
• spargere (to scatter or spill in small bits)
  But in everyday speech versare is perfectly natural for water.

The colon in Italian can introduce an explanation or cause just like perché (“because”). It’s more concise and often used in written or semi-formal contexts:

• Ti prego, non versare l’acqua: il tavolo è già un po’ bagnato.
  Equivalent with perché:
• Ti prego, non versare l’acqua perché il tavolo è già un po’ bagnato.