Learn Hardcore Portuguese (Portugal): Ao instalar uma nova aplicação, leio as condições com atenção antes de aceitar. - When installing a new app, I read the terms carefully before accepting.

Ao here is a contraction of a + o, literally to + the, but in this structure it doesn’t translate literally.
In ao + infinitive it usually means when, while, or upon doing something.
So ao instalar is best understood as when (I) install / upon installing rather than to the install.

Why is it ao instalar and not something like quando instalo?

Both are possible, but they’re slightly different:

Ao instalar uma nova aplicação… = When(ever) I install / Upon installing a new app…
- Focus on the action that happens at the same time or immediately after another.
Quando instalo uma nova aplicação… = When I install a new app…
- Slightly more neutral “whenever/when”.

In many contexts they can be exchanged with almost no change in meaning.
Ao + infinitive is very common in Portuguese for “when/while doing”.

Why is instalar in the infinitive and not instalo or another conjugated form?

In Portuguese, after a preposition like a (in ao) you must use the infinitive form of the verb.
So:

ao instalar = on/when installing
not ao instalo.

English uses a finite verb (“when I install”), but Portuguese uses a non‑finite form (instalar) in this structure.

Is ao instalar the same as an English -ing form like “installing”?

Functionally, yes, in this sentence.
Portuguese doesn’t use its gerúndio (instalando) as much as English uses -ing.
Instead, it very often uses ao + infinitive to express “when/while/upon doing”:

Ao instalar uma nova aplicação… ≈ When installing / Upon installing a new application…

You’ll sound more natural in European Portuguese with ao + infinitivo than with instalando here.

In European Portuguese, is aplicação really the normal word for a computer/phone app?

Yes. In European Portuguese, uma aplicação commonly means an application / an app (software).
In Brazilian Portuguese, people much more often say um aplicativo or just um app.
Be aware that aplicação also has other meanings in Portuguese, like application in the sense of use or application of a cream/paint, so the context matters.

Is there any nuance between uma nova aplicação and uma aplicação nova?

Both are grammatically correct, but the nuance can shift:

uma nova aplicação usually suggests a new/another application, focusing more on “new to you / additional”.
uma aplicação nova tends to highlight that the application itself is brand new, not old or used.

In everyday speech, people often say uma nova aplicação for “a new app”, and the difference is subtle.

Why is there no eu in leio as condições? How do we know it means “I read”?

Portuguese verb endings usually make the subject clear, so subject pronouns are often dropped.
Leio is the 1st person singular form of ler (to read), so it can only mean “I read” in this context.
You could say Eu leio as condições…, but that adds emphasis on “I” (as opposed to someone else).
The version without eu is more neutral and completely normal.

What is the time meaning of leio here? Is it like English present simple?

Yes. Leio is the present indicative and here it expresses a habitual action:

Leio as condições… = I (usually/always) read the terms…

Portuguese present can also refer to near future or general truths, but in this sentence it clearly describes what the speaker habitually does.

What does com atenção add to leio as condições? Could I say leio as condições atentamente instead?

Com atenção literally means “with attention”, so:

leio as condições com atenção = I read the terms carefully / attentively.

You can also say:

leio as condições atentamente.

Both are correct.
Com atenção is very common and slightly more neutral; atentamente can feel a bit more formal or bookish, and it’s also used as a polite sign‑off in letters/emails (Atentamente, = Sincerely).

Why is it antes de aceitar and not something like antes de que eu aceite?

Portuguese generally prefers preposition + infinitive in this kind of structure:

antes de aceitar = before accepting / before I accept.

A construction like antes que eu aceite (with que and the subjunctive) exists but is more restricted and sounds more formal/literary or is used when you want to emphasize a condition.
In everyday European Portuguese, antes de + infinitive is by far the most common: antes de sair, antes de comer, antes de aceitar, etc.

Where did the object go in antes de aceitar? Should it be antes de aceitar as condições or something like antes de as aceitar?

In the sentence:

Leio as condições com atenção antes de aceitar.

the object as condições is understood from the previous clause, so it’s omitted in antes de aceitar.
You could make it explicit in a few ways:

Leio as condições com atenção antes de aceitar as condições. (repeats the noun)
Leio as condições com atenção antes de as aceitar. (using a pronoun as = “them”)

In European Portuguese, antes de as aceitar is very natural.
The pronoun doesn’t go between de and aceitar as a separate word; it attaches closely to the verb: de as aceitar (often written together in speech rhythm) or de aceitá‑las (more common in Brazil/very formal styles).

Why is condições plural? Could it be singular condição?

It’s plural because it refers to the many individual clauses/points in the terms and conditions.
Typically you see phrases like:

as condições de utilização – the terms of use
os termos e condições – the terms and conditions

You could say a condição for a single specific condition (e.g. “one condition of the contract”), but for app/website legal text, the plural condições is the standard.