Learn Hardcore Portuguese (Brazil): Quando eu chegar, vou lhe mostrar o documento no aplicativo. - When I arrive, I will show you the document in the app.

Portuguese uses the future subjunctive after time words like quando when referring to a future event that hasn’t happened yet: Quando eu chegar (when I arrive). Quando eu chego is simple present and describes habitual/repeated actions, e.g., Quando eu chego em casa, janto (When I get home, I have dinner).

How do I form the future subjunctive in Portuguese?

Take the third-person plural preterite (eles/elas), drop -am, and add:

eu/você/ele/ela: the base form (often looks like the infinitive), e.g., chegar
tu: chegares
nós: chegarmos
vocês/eles/elas: chegarem

Examples:

chegaram → chegar, chegares, chegarmos, chegarem
Common irregulars: fizer (fazer), puder (poder), for (ir/ser), estiver (estar), vier (vir), souber (saber)

Can I omit the subject “eu”?

Yes. Quando chegar, vou lhe mostrar... is natural. Portuguese often drops subject pronouns when understood from context. Both clauses share the same subject, so repeating eu before vou is optional: Quando eu chegar, (eu) vou...

Why use vou mostrar instead of mostrarei?

In Brazilian Portuguese, ir + infinitive (e.g., vou mostrar) is the most common future in speech. Mostrarei (simple future) is correct but sounds more formal or written. Both mean the future; vou mostrar often feels more immediate or planned.

What exactly does lhe mean here?

Lhe is an indirect object pronoun meaning to you (singular, formal/neutral), to him, or to her. In this sentence it corresponds to English “you” in “show you.” The direct object is o documento. Plural is lhes (to you all/to them).

Is lhe common in Brazil? What are natural alternatives?

It varies by region and formality.

Very common in Brazil: vou te mostrar (with tu) or vou mostrar para você / pra você (with você).
Vou lhe mostrar is correct and used, but can sound formal or regional (e.g., parts of the South/Northeast). Many speakers avoid lhe with você in casual speech.

Where does the pronoun go—vou lhe mostrar, vou te mostrar, mostrar-lhe…?

Most natural in Brazil with compound futures: pronoun before the main verb: vou te mostrar / vou lhe mostrar.
After the infinitive with a hyphen (vou mostrar-te / vou mostrar-lhe) sounds European or formal.
With the simple future, postverbal is very formal: mostrarei-te / mostrarei-lhe.
With negation, put the pronoun after não: Não vou te mostrar / Não vou lhe mostrar.
Avoid te vou mostrar in Brazil; it sounds off.

Could I replace o documento with a pronoun (“it”)?

Yes:

Vou mostrá-lo (masc. singular, replacing o documento).

Notes:

After verbs ending in -r, -s, -z, the final consonant drops and the pronoun becomes -lo/-la/-los/-las; an accent may appear to keep stress: mostrar + o → mostrá-lo.
This hyphenated style is common in writing. In everyday Brazilian speech, people often prefer Vou te mostrar o documento or Vou mostrar o documento pra você.

Why is it no aplicativo? What does no mean?

No = em + o (in/on the). So no aplicativo means “in/on the app.” Feminine would be na (em + a), e.g., na plataforma. You can also say pelo aplicativo (por + o = through/by the app) for the idea of channel or means.

Is aplicativo the same as aplicação?

In Brazil, aplicativo (often shortened to app) is what you install on your phone. Aplicação is broader (a software application in some technical contexts) or non-tech meanings (e.g., a financial investment). For a phone app, say aplicativo.

Can I move no aplicativo elsewhere in the sentence?

Yes, but keep it natural:

Most common: Vou lhe mostrar o documento no aplicativo.
Also possible: Vou lhe mostrar, no aplicativo, o documento (more formal) or Vou lhe mostrar no aplicativo o documento. Placing no aplicativo at the end is the safest and most neutral.

Why is there a comma after Quando eu chegar?

When an adverbial clause (like a time clause introduced by quando) comes first, Portuguese uses a comma: Quando eu chegar, ... If the main clause comes first, the comma is usually omitted: Vou lhe mostrar o documento no aplicativo quando eu chegar.

Shouldn’t chegar take a preposition like a or em?

Only when a place is expressed. Here it’s implicit (“when I arrive [there]”). If you mention the place:

Colloquial Brazil: chegar em — Quando eu chegar em casa...
More formal/standard: chegar a — Quando eu chegar à empresa... (crase: a + a = à), ao trabalho (a + o = ao).

Pronunciation tips for key words in the sentence

Quando: “KWAN-doo” (nasal an).
eu: “eh-oo” (quick glide).
chegar: “sheh-GA(h)/sheh-GAɾ” (ch like “sh”; final r varies by region).
vou: “voh”.
lhe: “LYE” (palatal lh, like “lli” in “million”).
mostrar: “mos-TRA(h)/mos-TRAɾ” (stress on last syllable).
documento: “doo-koo-MEN-to”.
aplicativo: stress on “ti”; in much of Brazil t before i can sound like “ch”: “ah-plee-kah-CHEE-vo”.

What’s the difference between quando and se here?

Quando eu chegar = when I arrive (assumes the arrival will happen).
Se eu chegar = if I arrive (uncertain). Use se for conditions, quando for time.

Could I say Quando eu chegar, eu te mostro?

Yes—very natural in speech. The future meaning is carried by quando eu chegar (future subjunctive), so the main clause can be in the present: eu te mostro. You can also use the periphrastic future: vou te mostrar.

Why o documento and not um documento?

O documento (the document) refers to a specific document known or identifiable in context. Um documento (a document) would be non-specific. Both are grammatical; choose based on whether the document is definite/specific.

How would this change for plural “you”?

Use lhes (to you all): Quando eu chegar, vou lhes mostrar o documento no aplicativo. Very common alternative in Brazil: vou mostrar o documento para vocês (or pra vocês).

Is Quando eu chegar, vou mostrar-lhe... wrong in Brazil?

Not wrong, but it sounds European or quite formal. Brazilian Portuguese strongly prefers the pronoun before the main verb in this structure: vou lhe mostrar or vou te mostrar.