Bevo solo acqua pura.

Bevo is the first-person singular present tense form of bere (to drink).

So:

• bere = to drink
• io bevo = I drink / I am drinking

In Italian, the simple present often covers both I drink and I am drinking, depending on context.

Italian often drops subject pronouns when they are not needed.

Because bevo already tells you the subject is I, adding io is usually unnecessary.

• Bevo solo acqua pura. = normal, natural
• Io bevo solo acqua pura. = also correct, but more emphatic, as if you are stressing I

Italian does this much more often than English.

In Italian, when talking about something in a general sense, especially with food and drink, you often do not use an article.

So:

• Bevo acqua. = I drink water.
• Mangio pane. = I eat bread.

Here, acqua pura is treated as an uncountable substance, so no article is needed.

If you used an article, it would usually sound more specific:

• Bevo l’acqua pura di quella sorgente. = I drink the pure water from that spring.

Here solo means only, and it is limiting what the speaker drinks.

So the sentence means that the only thing the speaker drinks is pure water.

Placing solo before acqua pura is very natural:

• Bevo solo acqua pura.

You may also hear:

• Bevo soltanto acqua pura.

That means the same thing, with soltanto being a slightly fuller version of solo.

Not in this sentence.

Here solo is an adverb, meaning only, so it does not agree with acqua.

• solo = only

So:

• Bevo solo acqua pura. = correct

If solo were being used as an adjective, then it could change form:

• solo uomo = only man / lone man
• sola donna = only woman / lone woman

But that is not what is happening here.

Because pura is an adjective describing acqua, and adjectives usually agree with the noun in gender and number.

• acqua is feminine singular
• so the adjective must also be feminine singular

That gives:

• acqua pura

Compare:

• vino puro = pure wine
• acqua pura = pure water
• bevande pure = pure drinks

In Italian, many descriptive adjectives normally come after the noun.

So:

• acqua pura = pure water
• vino rosso = red wine
• pane fresco = fresh bread

Putting the adjective before the noun is sometimes possible, but it often sounds more literary, more emotional, or changes the emphasis. In this sentence, acqua pura is the standard and natural order.

Yes. Acqua is a feminine noun.

That is why, if you use an article, you get:

• l’acqua
• un’acqua

Even though it takes l’ before the vowel, the noun is still feminine, which is why the adjective is pura, not puro.

Yes, in practice it is usually understood that way.

English often has ambiguity with only, and Italian can have similar issues depending on emphasis. In this sentence, the most natural interpretation is:

• the only thing I drink is pure water

In normal conversation, that meaning is clear enough from context.

If someone wanted to emphasize something different, they could change the wording or stress.

Yes, absolutely.

Solo and soltanto both mean only here.

• Bevo solo acqua pura.
• Bevo soltanto acqua pura.

Both are correct and natural.
Soltanto can sound a little more formal or a little more explicit, but the difference is small.

Yes, it is natural and correct.

It sounds like a normal statement meaning that the speaker drinks nothing except pure water.

Depending on context, a native speaker might also say things like:

• Bevo solo acqua. = I only drink water.
• Bevo soltanto acqua naturale. = I only drink still/plain water.
• Bevo solo acqua molto pura. = I only drink very pure water.

But Bevo solo acqua pura is perfectly good Italian.

It can be either, depending on context.

Italian present tense often covers both ideas:

• I drink
• I am drinking

So Bevo solo acqua pura could mean:

• a general habit: I only drink pure water
• what is happening now: I’m only drinking pure water

If Italian needs to be very explicit about an action in progress, it can use stare + gerundio, but that is not necessary here.

For example:

• Sto bevendo solo acqua pura. = I am drinking only pure water.