Eu vou pagar a fatura agora e depois vou ao supermercado.

Yes, you often can.

In Brazilian Portuguese, the verb form usually already shows the subject, so eu is optional here. A very natural spoken version is:

Vou pagar a fatura agora e depois vou ao supermercado.

Using eu can add:

• emphasis
• clarity
• contrast with someone else

So Eu vou pagar... is correct, but Vou pagar... is also very common.

Vou pagar is the most common everyday way to talk about the near future in Brazilian Portuguese.

It is formed with:

• vou = I am going
• infinitive verb = pagar

So vou pagar literally looks like I am going to pay, and that is exactly how it often works.

The simple future pagarei is grammatically correct, but it sounds:

• more formal
• more written
• less conversational in many everyday situations

So in normal speech, vou pagar is usually the more natural choice.

Because the two vou forms are doing different jobs.

In vou pagar:

• vou is an auxiliary helping form the future
• pagar is the main verb

In vou ao supermercado:

• vou itself is the main verb, from ir
• it means I go / I’m going / I’ll go, depending on context

So vou ir ao supermercado is usually avoided in standard usage because it sounds repetitive: basically I’m going to go.

Portuguese normally prefers:

• vou pagar
• vou ao supermercado

Ao is a contraction of:

• a = to
• o = the

So:

• a + o = ao

That means ao supermercado is literally to the supermarket.

This contraction is required in standard Portuguese. You do not normally say a o supermercado.

In Portuguese, it is very common to use a definite article with places like o supermercado, o banco, o hospital, o cinema.

So after ir a, you usually get:

• ir ao supermercado
• ir ao banco
• ir ao cinema

Saying vou a supermercado sounds incomplete or unnatural in standard Portuguese.

Because the subject is still the same: I.

Portuguese often omits repeated subject pronouns when the meaning is clear. So:

Eu vou pagar a fatura agora e depois vou ao supermercado.

is perfectly natural.

You could also say:

Eu vou pagar a fatura agora e depois eu vou ao supermercado.

That is also correct, but the second eu is not necessary unless you want emphasis.

They show the order of actions.

• agora = now
• depois = afterward / later / then

So the sequence is:

1. pay the bill now
2. go to the supermarket after that

They help organize the timeline very clearly.

Yes. Portuguese allows some flexibility in adverb placement.

For example, these are all possible:

• Eu vou pagar a fatura agora e depois vou ao supermercado.
• Agora eu vou pagar a fatura e depois vou ao supermercado.
• Eu vou agora pagar a fatura e depois vou ao supermercado.
  (less common in everyday speech)
• Eu vou pagar a fatura e depois vou ao supermercado.

The original version sounds very natural and clear.

Not always.

In Brazilian Portuguese:

• fatura often refers to an invoice or a bill to be paid, especially things like a credit card bill
• conta is a broader word and can mean a bill, account, or tab

Examples:

• fatura do cartão = credit card bill
• conta de luz = electricity bill
• conta do restaurante = restaurant bill/check

So fatura is correct, but the exact English equivalent depends on context.

E simply means and. It connects the two actions:

• vou pagar a fatura agora
• depois vou ao supermercado

You could also separate them into two sentences:

Eu vou pagar a fatura agora. Depois vou ao supermercado.

But using e depois makes the flow smoother in one sentence.

Yes, but there is a slight difference in feel.

• ir ao supermercado is the most standard and common way to say go to the supermarket
• ir para o supermercado can also work, but it may emphasize the destination a bit more

In many everyday situations, both are understood. However, vou ao supermercado is the most natural textbook-standard choice here.

Yes, it is natural and correct.

A very common spoken version would be:

Vou pagar a fatura agora e depois vou ao supermercado.

That sounds normal and everyday in Brazil. The version with eu is also correct; it just feels a little more explicit.