Depois do jantar, nós comemos melão e bebemos água.

Do is a contraction of de + o.

• de = of / from / after in some expressions
• o = the

So depois do jantar is literally after the dinner, but in natural English it is usually just after dinner. In Portuguese, using the article with meal words is very common.

Yes. Both are natural, but there is a small difference:

• depois do jantar = after the dinner / after dinner, treating jantar as a noun
• depois de jantar = after having dinner / after dinner, with a more verbal idea

In European Portuguese, both are used. Depois de jantar is especially common in everyday speech.

The comma separates the introductory time phrase from the main clause.

• Depois do jantar, = sets the time first
• nós comemos melão e bebemos água = the main action

This is similar to English: After dinner, we ate melon and drank water.
Without the comma, the sentence would still be understandable, but the comma is very natural.

No, it is not necessary.

Portuguese often drops subject pronouns because the verb ending already shows who is doing the action. So you can say:

• Depois do jantar, nós comemos melão e bebemos água.
• Depois do jantar, comemos melão e bebemos água.

Both are correct. Nós may be used for emphasis, clarity, or contrast. In European Portuguese, leaving it out is very common.

They are the first-person plural forms, matching nós = we.

• comemos comes from comer = to eat
• bebemos comes from beber = to drink

For regular -er verbs, the nós form in the present tense usually ends in -emos:

• comer → comemos
• beber → bebemos

So these forms match we eat / we drink or, depending on context, we ate / we drank.

It can be either, depending on context.

For many regular -er verbs, the nós form is identical in:

• the present indicative
• the preterite (simple past)

So:

• comemos can mean we eat or we ate
• bebemos can mean we drink or we drank

You usually know which one is meant from the wider context. The sentence by itself is grammatically ambiguous.

Because after verbs like comer and beber, Portuguese often uses a noun without an article when speaking in a general or indefinite way.

So:

• comemos melão = we ate melon / we ate some melon
• bebemos água = we drank water

If you add the article, it usually sounds more specific:

• comemos o melão = we ate the melon
• bebemos a água = we drank the water

So the version without articles is very natural here.

No, not completely.

The sentence begins with Depois do jantar to establish the time first. But you could also say:

• Nós comemos melão e bebemos água depois do jantar.

That is also correct. The main difference is emphasis and rhythm, not basic meaning.

A rough guide is:

duh-POYSH du zhan-TAR, nozh ku-MEH-moosh meh-LOWN i bu-BEH-moosh AH-gwa

A few useful pronunciation points:

• depois ends roughly like sh
• j in jantar sounds like the s in measure
• ão in melão is nasal
• água is stressed on the first syllable: Á-gua

European Portuguese often reduces unstressed vowels, so the spoken sentence can sound more compact than the spelling suggests.

Yes, in informal speech, but the verb must change to third-person singular.

So you would say:

• Depois do jantar, a gente come melão e bebe água.

Not:

• a gente comemos
• a gente bebemos

In European Portuguese, nós is standard and very common. A gente also exists, but it is more informal.