Quando eu for ao Porto, quero conhecer melhor a cidade.

Because this sentence is talking about a future event after quando.

In Portuguese, when quando refers to the future, it usually takes the future subjunctive, not the ordinary future or present form. So:

• Quando eu for ao Porto... = When I go to Porto...
• not Quando eu vou ao Porto... in this meaning

Here, for is the future subjunctive of ir.

A very common pattern is:

• quando + future subjunctive
• se + future subjunctive
• logo que + future subjunctive
• assim que + future subjunctive

Examples:

• Quando eu tiver tempo, telefono.
• Se eu puder, vou.

So for is correct because the action of going to Porto has not happened yet.

For is the future subjunctive form of the verb ir for eu.

The future subjunctive of ir is:

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

So in the sentence:

• Quando eu for ao Porto...

the verb is ir, not ser, even though for also looks like a form of ser in other contexts.

That can be confusing, because Portuguese has forms that look identical:

• se eu for can mean if I go or if I am
• the meaning depends on context

Here, because of ao Porto, it clearly means go to Porto, so it comes from ir.

Ao is a contraction of:

• a = to
• o = the

So:

• a + o = ao

This happens because Porto commonly takes the masculine definite article o in Portuguese:

• o Porto

So:

• ir a o Porto becomes ir ao Porto

This is very natural Portuguese.

Many place names in Portuguese are used with a definite article, even when English does not use one.

So in Portuguese, the city is often:

• o Porto

That is why you get:

• no Porto = in Porto
• do Porto = from/of Porto
• ao Porto = to Porto

This is something you usually just learn city by city or place by place. Not all place names behave the same way.

For example:

• Lisboa usually appears without an article: vou a Lisboa
• Porto often appears with one: vou ao Porto

This is one of those usage patterns that learners need to get used to.

Because the wanting exists now.

The sentence means that right now the speaker has that wish or intention:

• Quero conhecer melhor a cidade. = I want to get to know the city better.

The going to Porto is future:

• Quando eu for ao Porto...

But the desire is present:

• quero

This is very natural in both Portuguese and English.

Compare:

• When I go to Porto, I want to explore the city more.

The going is future, but the wanting is already true now.

Here conhecer means something like:

• to get to know
• to become familiar with
• to explore
• sometimes to see/visit in context

Portuguese has an important difference between:

• saber = to know a fact, know how
• conhecer = to know a person/place, be familiar with

So:

• Sei a resposta. = I know the answer.
• Conheço o Porto. = I know Porto / I am familiar with Porto.

In this sentence, conhecer melhor a cidade suggests becoming more familiar with the city, probably by visiting or exploring it.

Because melhor here works as an adverb meaning better and it normally comes after the infinitive or verb phrase in this type of sentence.

So:

• quero conhecer melhor a cidade

means:

• I want to know the city better
• I want to get to know the city better

This is the normal word order.

If you moved melhor, it could sound unnatural or mean something different depending on context. For this sentence, conhecer melhor is the standard expression.

Melhor means better, but in this context it usually implies:

• more thoroughly
• more deeply
• more completely

So conhecer melhor a cidade does not necessarily mean the speaker already knows the city very well. It can simply suggest wanting to explore it more, understand it more, or become more familiar with it.

It is a very common phrase in Portuguese:

• quero conhecer melhor Portugal
• quero conhecer melhor esta zona
• quero conhecer-te melhor

Because once Porto has already been mentioned, Portuguese can naturally refer back to it as a cidade.

So:

• Quando eu for ao Porto, quero conhecer melhor a cidade.

means:

• When I go to Porto, I want to get to know the city better.

Using a cidade avoids repetition and sounds natural.

It is similar to English:

• When I go to Porto, I want to get to know the city better.

Not always. Portuguese often drops subject pronouns because the verb ending already shows the person.

So you could also say:

• Quando for ao Porto, quero conhecer melhor a cidade.

That is perfectly natural.

However, eu may be included:

• for clarity
• for emphasis
• because the speaker simply prefers it

So both are correct:

• Quando eu for ao Porto...
• Quando for ao Porto...

Not in this structure.

After quando with a future meaning, Portuguese normally uses the future subjunctive, not the simple future indicative.

So:

• Quando eu for ao Porto... ✅
• Quando eu irei ao Porto... ❌ in standard usage for this meaning

This is a very important rule in Portuguese. English often uses a present form after when, but Portuguese uses the future subjunctive in these cases.

Yes, mainly in the sense that it fits very naturally with European Portuguese usage, especially:

• ao Porto, because Porto commonly takes the article o
• the overall structure is fully standard in Portugal

The grammar itself is not uniquely European, because the future subjunctive is also used in Brazilian Portuguese. But article usage with place names can vary a bit by region and habit.

For a learner of Portuguese from Portugal, this sentence is completely natural and standard.

Portuguese and English organize this idea a little differently.

Portuguese:

• Quando eu for ao Porto, quero conhecer melhor a cidade.

Natural English:

• When I go to Porto, I want to get to know the city better.

The main differences are:

• Portuguese uses future subjunctive: quando eu for
• English uses a present form after when: when I go
• Portuguese uses conhecer for becoming familiar with a place
• ao Porto includes the article that English does not use

So even though the meaning is straightforward, the grammar does not match English word for word.