Quando vejo uma curva, eu deixo de acelerar.

Vejo is the 1st person singular present tense of ver (to see), so it means I see.

• eu vejo = I see
• tu vês = you see
• ele/ela vê = he/she sees

There is no reflexive meaning here, so vejo-me would mean I see myself, which is not what this sentence says.

In Portuguese, the present tense is often used for habits, general truths, and things that regularly happen.

So:

• Quando vejo uma curva, eu deixo de acelerar.

means something like:

• When I see a bend, I stop accelerating
• Whenever I see a bend, I stop accelerating

It describes a repeated or typical action, not just one single moment.

Here, quando means when.

In this sentence, it introduces a time clause:

• Quando vejo uma curva = When I see a bend / Whenever I see a bend

Because the sentence is about a repeated situation, English often naturally translates it as whenever.

Uma curva literally means a curve, but in driving context it usually means:

• a bend
• a curve in the road
• sometimes a turn

For a learner of European Portuguese, curva is a very natural road/driving word.

Examples:

• A estrada tem muitas curvas. = The road has many bends.
• Abranda antes da curva. = Slow down before the bend.

Portuguese often uses articles where English may or may not use them.

• uma curva = a curve / a bend

Here, uma introduces a singular countable noun in a normal way. It refers to a bend in general, not a specific one already known to the listener.

If you said just vejo curva, it would sound incomplete or unnatural in standard Portuguese.

Deixar de + infinitive means to stop doing something, to cease doing something, or to no longer do something.

So:

• deixo de acelerar = I stop accelerating

It does not necessarily mean I brake. It specifically means that I stop pressing the accelerator / stop increasing speed.

That is an important distinction:

• deixar de acelerar = stop accelerating
• travar / travar a fundo / pôr o pé no travão = brake

Yes, it is very common and natural.

Some examples:

• Deixei de fumar. = I stopped smoking.
• Ele deixou de estudar. = He stopped studying.
• Nós deixámos de ir lá. = We stopped going there.

In European Portuguese, this structure is very normal in both spoken and written language.

Yes, but deixo de acelerar is generally the more idiomatic choice here.

Compare:

• deixo de acelerar = I stop accelerating
• paro de acelerar = understandable, but less natural in many contexts

In Portuguese, parar de + infinitive also exists and is correct:

• Parei de fumar. = I stopped smoking.

But with something like driving, deixar de acelerar often sounds smoother and more idiomatic.

Yes, Portuguese often omits subject pronouns because the verb ending already shows the subject.

So both are possible:

• Quando vejo uma curva, deixo de acelerar.
• Quando vejo uma curva, eu deixo de acelerar.

The version with eu may add:

• a little emphasis
• clarity
• a more explicit rhythm in speech

In many cases, especially in European Portuguese, leaving out eu is very common unless you want contrast or emphasis.

The comma is standard and helpful here because the sentence begins with a subordinate clause:

• Quando vejo uma curva, ...

Then comes the main clause:

• ... eu deixo de acelerar.

So the comma separates:

1. the when-clause
2. the main statement

This is very natural punctuation in Portuguese.

Not exactly.

Eu deixo de acelerar means:

• I stop accelerating
• I stop speeding up

That does not always mean the car becomes slower immediately. It simply means you are no longer increasing speed.

If you wanted I slow down, Portuguese would more naturally use:

• abrando
• reduzo a velocidade
• desacelero in some contexts

So the original sentence is more precise than I slow down.

The infinitive is acelerar (to accelerate).

After deixar de, Portuguese uses the infinitive:

• deixar de acelerar = to stop accelerating

This is a very common pattern:

• deixar de comer = stop eating
• deixar de falar = stop talking
• deixar de trabalhar = stop working

So the structure is:

• deixar
  • de
    • infinitive

It would sound perfectly natural:

• Quando vejo uma curva, deixo de acelerar.

In fact, many speakers of European Portuguese would probably prefer this version in everyday speech unless they want to stress I.

So:

• with eu = slightly more explicit or emphatic
• without eu = very natural, often more typical

Yes, a few useful points:

1. Dropping subject pronouns is very common in European Portuguese.
   So deixo de acelerar is often enough without eu.

2. Deixar de + infinitive is a very natural structure in Portugal.
   It is worth learning as a fixed pattern.

3. Curva is a common everyday driving word in Portugal for a road bend.

4. The sentence sounds neutral and natural in European Portuguese.
   It is the kind of structure you could hear in driving advice, conversation, or instruction.

Yes, and that is probably the most natural interpretation.

Because both verbs are in the present tense, the sentence usually expresses a habitual reaction:

• Whenever I see a bend, I stop accelerating.

If you wanted a single past event, Portuguese would normally change the tense:

• Quando vi uma curva, deixei de acelerar.
  = When I saw a bend, I stopped accelerating.