Cuando el cielo está despejado, me concentro mejor y voy al campus a pie.

Because cuando without an accent is used as a conjunction meaning when in statements:

• Cuando el cielo está despejado... = When the sky is clear...

Cuándo with an accent is used in questions or indirect questions:

• ¿Cuándo vas al campus? = When do you go to campus?
• No sé cuándo va al campus. = I don’t know when he goes to campus.

So here, since it introduces a time clause in a normal statement, cuando is correct.

In Spanish, the definite article is often used more than in English. El cielo literally means the sky, and that is the normal way to say it.

English sometimes drops articles where Spanish keeps them, but with nouns like this, Spanish usually uses one:

• el cielo
• el sol
• la luna

So cielo by itself would sound incomplete here.

This is a classic ser vs estar question.

Spanish uses estar for a state or condition, especially one that can change. A sky being clear is seen as a current condition, so:

• El cielo está despejado = The sky is clear

Using ser here would sound unnatural because despejado is not being treated as an essential, permanent characteristic of the sky.

Compare:

• Está nublado = It’s cloudy
• Está despejado = It’s clear

These are weather conditions, so estar is the normal choice.

Here, despejado means clear, as in free of clouds.

In other contexts, despejado can also mean things like:

• un lugar despejado = an open / uncluttered place
• una mente despejada = a clear mind

So the core idea is clear, free, or unblocked, but in this sentence it specifically refers to the weather.

Yes. The usual verb is concentrarse for to concentrate.

So:

• me concentro = I concentrate
• literally, something like I concentrate myself, though you should not translate it word for word in normal English

The reflexive pronouns are:

• me
• te
• se
• nos
• os
• se

Examples:

• Me concentro mejor por la mañana. = I concentrate better in the morning.
• ¿Te concentras en clase? = Do you concentrate in class?

In this sentence, me matches the first-person singular verb form concentro.

Because mejor is the comparative form of bien and means better.

• bien = well
• mejor = better

So:

• Me concentro bien = I concentrate well
• Me concentro mejor = I concentrate better

Más bien is a different expression and usually means something like rather or more like in other contexts, so it would not fit here.

Spanish often leaves out subject pronouns because the verb ending already shows who the subject is.

• me concentro clearly means I concentrate
• voy clearly means I go

So yo is unnecessary unless you want emphasis or contrast:

• Yo me concentro mejor, pero ella no. = I concentrate better, but she doesn’t.

In neutral sentences, omitting yo sounds more natural.

Al is the contraction of a + el.

So:

• voy al campus = voy a el campus → contracted to al

This contraction is required whenever a is followed by the masculine singular article el.

The same happens with de + el = del:

• vengo del campus = I come from the campus

Important exception: if El is part of a proper name, you do not contract it:

• Voy a El Escorial.
  Not al Escorial

Because a pie is the fixed expression meaning on foot or walking.

• ir a pie = to go on foot
• volver a pie = to return on foot

Examples:

• Voy al trabajo a pie. = I go to work on foot.
• Prefiero ir a pie. = I prefer to go on foot.

En pie means something different: standing.

• Estoy en pie. = I am standing.

So in this sentence, a pie is the only natural choice.

The sentence describes a habitual or general situation, so Spanish uses the present tense:

• Cuando el cielo está despejado, me concentro mejor y voy al campus a pie.

This means something like:

• Whenever the sky is clear, I concentrate better and walk to campus.

It is not talking about one single event, but about a repeated pattern.

Not necessarily. This is an important point.

In this sentence, cuando + present works because it expresses a habitual idea.

But if you mean a specific future situation, Spanish often uses cuando + subjunctive:

• Cuando el cielo esté despejado, iré al campus a pie.
  = When the sky is clear, I’ll go to campus on foot.

So compare:

• Cuando el cielo está despejado, voy al campus a pie.
  = Whenever the sky is clear, I go on foot.
• Cuando el cielo esté despejado, iré al campus a pie.
  = When the sky is clear (in the future), I’ll go on foot.

That contrast is very useful to learn early.

Because the sentence begins with a time clause:

• Cuando el cielo está despejado, ...

In Spanish, it is very common to put a comma after an introductory subordinate clause, especially when it comes first.

If the main clause came first, the comma would usually disappear:

• Me concentro mejor y voy al campus a pie cuando el cielo está despejado.

Both versions are correct, but the original structure puts the time condition first for emphasis.

Yes, campus is used in Spanish, including in Spain, especially in university contexts.

So:

• ir al campus = to go to campus

However, depending on context, people might also say:

• voy a la universidad = I go to university / to the university
• voy a la facultad = I go to my faculty/building/school within the university

So campus is fine, but it is one of several possible word choices depending on exactly what you mean.