O menino dorme agora.

Yes. O is the masculine singular definite article, so here it means the.

• o menino = the boy
• a menina = the girl

In Portuguese, articles are used very often, sometimes more often than in English.

Because menino is the masculine form meaning boy, while menina is the feminine form meaning girl.

• menino = boy
• menina = girl

The article changes too:

• o menino = the boy
• a menina = the girl

Dorme is the third-person singular form of the verb dormir (to sleep / to be sleeping, depending on context).

Present tense of dormir:

• eu durmo = I sleep
• você/ele/ela dorme = you/he/she sleeps
• nós dormimos = we sleep
• vocês/eles/elas dormem = you/they sleep

So o menino dorme literally corresponds to the boy sleeps.

In Portuguese, the simple present can often express something happening right now, especially when a time word like agora is present.

So:

• O menino dorme agora. = The boy is sleeping now.
• O menino está dormindo agora. = The boy is sleeping now.

In Brazilian Portuguese, está dormindo can sound a bit more explicitly ongoing, but dorme agora is still understandable and natural in many contexts.

Agora means now. It gives the time reference and helps show that the action is happening at the present moment.

So:

• O menino dorme. = The boy sleeps / The boy is sleeping.
• O menino dorme agora. = The boy is sleeping now.

Yes. Portuguese allows some flexibility with adverbs like agora.

These are possible:

• O menino dorme agora.
• Agora o menino dorme.
• O menino agora dorme.

They all relate to now, but the emphasis can change slightly. The most neutral version here is O menino dorme agora.

Normally, no. In standard Portuguese, you usually need the article here.

• natural: O menino dorme agora.
• unnatural in this context: Menino dorme agora.

Leaving out the article may sound incomplete or headline-like, not like a normal everyday sentence.

Because the noun o menino is already the subject, so a pronoun is not needed.

• O menino dorme agora. = The boy is sleeping now.

You could say Ele dorme agora if the context already makes it clear who he is, but if you want to identify the person as the boy, you use o menino.

A simple approximate pronunciation for an English speaker is:

oo meh-NEE-noh DOR-mee ah-GOH-rah

A few helpful notes:

• menino has stress on ni: me-NI-no
• dorme has stress on dor: DOR-me
• agora usually has stress on go: a-GO-ra

The r in agora varies by region in Brazil, but the stressed syllable is the important part to notice first.

Not exactly. In Brazilian Portuguese, the r sound is different from the English r.

In dorme, the r is inside the word, and in many Brazilian accents it sounds like a light tapped or flipped sound, somewhat like the quick sound in the American English pronunciation of butter for some speakers.

You do not want a strong English r.

Yes. The Portuguese present tense can cover both ideas, and context tells you which one is meant.

• The boy sleeps now is less natural in English in many situations.
• English usually prefers The boy is sleeping now for an action happening at this moment.

Portuguese does not always need a separate progressive form the way English often does.

Yes. This is the basic and most common order:

subject + verb + time expression

• O menino = subject
• dorme = verb
• agora = time word

So O menino dorme agora is a very standard sentence structure in Portuguese.