Se a reunião for na sexta-feira, vou ao banco depois do almoço.

Because Portuguese usually uses the future subjunctive after se when talking about a possible future situation.

So:

• Se a reunião é na sexta-feira sounds wrong for this meaning.
• Se a reunião for na sexta-feira = If the meeting is on Friday

Here, for is the future subjunctive of ser.

This is a very common pattern in Portuguese:

• Se eu tiver tempo, telefono-te. = If I have time, I’ll call you.
• Se chover, ficamos em casa. = If it rains, we’ll stay home.

So after se, when the condition refers to the future, Portuguese often uses:

• future subjunctive in the if-clause
• a present or future form in the main clause

In this sentence, for comes from ser, not ir.

That is because the sentence is saying the meeting is on Friday, not that it goes somewhere.

Compare:

• Se a reunião for na sexta-feira... → from ser = if the meeting is on Friday
• Se eu for ao banco... → from ir = if I go to the bank

The form for can belong to either verb, so the context tells you which one it is.

For is the future subjunctive.

For the verb ser, the future subjunctive forms are:

• se eu for
• se tu fores
• se ele/ela/você for
• se nós formos
• se vós fordes
• se eles/elas/vocês forem

This tense is very common in Portuguese, especially after words like:

• se = if
• quando = when
• logo que = as soon as
• assim que = as soon as

when they refer to the future.

Example:

• Quando ele chegar, começamos. = When he arrives, we’ll start.

English does not really have a separate future subjunctive form, so this often feels new to English speakers.

Both are possible, but vou ao banco is much more natural in everyday Portuguese.

In this sentence, vou is the present indicative, but it refers to a future action because the context makes that clear.

So:

• vou ao banco = I’m going to the bank / I’ll go to the bank
• irei ao banco = I will go to the bank

The simple future (irei) is correct, but it can sound more formal, deliberate, or less conversational.

In normal speech, Portuguese often uses the present tense for planned or expected future actions, especially when there is a time expression or a condition:

• Amanhã vou ao banco. = Tomorrow I’m going to the bank.
• Se tiver tempo, vou contigo. = If I have time, I’ll go with you.

Ao banco is a contraction of:

• a = to
• o = the

So:

• a + o = ao

That means:

• vou ao banco = I go to the bank / I’m going to the bank

This kind of contraction is extremely common in Portuguese:

• a + a = à
• de + o = do
• de + a = da
• em + o = no
• em + a = na

Examples:

• Vou à escola. = I’m going to the school.
• Venho do trabalho. = I come from work.
• Estou no banco. = I’m at the bank.

Na sexta-feira is a contraction of:

• em = on/in
• a = the

So:

• em + a = na

Literally, it is something like on the Friday, but in natural English you usually just say on Friday.

In Portuguese, days of the week commonly appear with the article in expressions like this:

• na segunda-feira = on Monday
• na terça-feira = on Tuesday
• na sexta-feira = on Friday

So for na sexta-feira means is on Friday.

Because Portuguese often uses the definite article where English does not.

Do almoço is a contraction of:

• de = of/from/after, depending on context
• o = the

So:

• depois do almoço = after lunch
  Literally: after the lunch

This is very normal in Portuguese. You will often see articles with meals, times of day, and many general nouns.

Examples:

• antes do jantar = before dinner
• depois do pequeno-almoço = after breakfast
• durante a manhã = during the morning

For a native English speaker, the article may feel unnecessary, but in Portuguese it is often the natural choice.

Usually, in standard Portuguese, depois do almoço is the safest and most natural choice here.

• depois do almoço = after lunch

You may sometimes hear reduced or less formal patterns in certain contexts, but for a learner, depois do almoço is the form to remember.

The same applies to similar expressions:

• antes do almoço
• depois do jantar
• antes do pequeno-almoço

The comma separates the conditional clause from the main clause:

• Se a reunião for na sexta-feira, = if the meeting is on Friday
• vou ao banco depois do almoço. = I’ll go to the bank after lunch

This is very common and natural in Portuguese, just as in English:

• If it rains, we’ll stay home.
• Se chover, ficamos em casa.

The comma helps show the structure clearly.

Yes. You can also say:

• Vou ao banco depois do almoço se a reunião for na sexta-feira.

This means the same thing.

When the if-clause comes first, a comma is normally used:

• Se a reunião for na sexta-feira, vou ao banco depois do almoço.

When the main clause comes first, the comma is often omitted:

• Vou ao banco depois do almoço se a reunião for na sexta-feira.

Yes, vou is grammatically present tense.

But in Portuguese, just like in English, the present tense can be used for future meaning when the context makes it clear.

Compare in English:

• If the meeting is on Friday, I’m going to the bank after lunch.

That is present form with future meaning.

Portuguese does the same:

• Se a reunião for na sexta-feira, vou ao banco depois do almoço.

So the time reference comes from the whole sentence, not only from the verb form.

In this sentence, yes, banco means a financial bank.

The word banco can also mean bench in other contexts, but ir ao banco very commonly means to go to the bank.

Context decides the meaning:

• Sentei-me no banco do jardim. = I sat on the park bench.
• Vou ao banco levantar dinheiro. = I’m going to the bank to withdraw money.

So in your sentence, the meaning is clearly the financial institution.

Yes, it is natural and grammatically correct in European Portuguese.

A European Portuguese speaker could definitely say:

• Se a reunião for na sexta-feira, vou ao banco depois do almoço.

A few points that fit European Portuguese well:

• use of for after se
• use of the present vou for a future plan
• use of articles in na sexta-feira and do almoço

So this is a good, natural model sentence for Portugal Portuguese.