Kiam ni pasas tra la koridoro, ni ĉiam vidas la sunon brili sur la muro.

Both are possible in practice, but in this sentence it is understood as whenever because the main clause contains ĉiam.

So:

• Kiam ni pasas tra la koridoro... literally looks like When we pass through the corridor...
• but ni ĉiam vidas... shows that this is a repeated, habitual action

So natural English would often be Whenever we pass through the corridor, we always see...

Esperanto often uses kiam in places where English might prefer either when or whenever, depending on context.

In Esperanto, the present tense is often used for:

• things happening now
• habitual actions
• general truths

Here it is a habitual action: every time this situation happens, the result is the same.

So ni pasas does not have to mean we are passing right now. In this context it means something more like:

• when we pass
• whenever we pass
• when we go through

The word ĉiam helps make that habitual meaning clear.

Tra means through. It shows movement from one side or part of a space to another, passing inside it.

So:

• tra la koridoro = through the corridor

This is a very natural choice with pasas, because pasi tra means to pass through.

Compare:

• en la koridoro = in the corridor
• tra la koridoro = through the corridor
• laŭ la koridoro = along the corridor

So pasas tra la koridoro is more precise than just saying we are in the corridor.

Because koridoro is the object of the preposition tra, not the direct object of the verb.

In Esperanto, nouns after prepositions usually do not take -n, because the preposition already shows the relationship.

So:

• tra la koridoro = correct
• en la domo = correct
• sur la tablo = correct

The -n ending is mainly for:

1. direct objects
2. direction in some cases without a preposition, or with certain expressions

Here, tra already clearly expresses movement through something, so no extra -n is needed on koridoro.

Because la sunon is the direct object of vidas.

The structure is:

• ni vidas la sunon brili

That means:

• we see the sun shine / shining

Even though the sun is the one doing the shining, it is still the thing being seen, so it gets the accusative -n:

• la sunon

This is very common after verbs of perception such as:

• vidi = to see
• aŭdi = to hear
• senti = to feel

Because after vidas, Esperanto often uses an infinitive to show what the object is doing.

So:

• ni vidas la sunon brili = we see the sun shining

This pattern is very common:

• Mi aŭdas la birdon kanti = I hear the bird singing
• Ni vidas ilin kuri = We see them running

If you said brilas, you would have a separate finite verb, and the sentence would need a different structure, such as:

• Ni vidas, ke la suno brilas sur la muro = We see that the sun is shining on the wall

That is also correct, but it is a different construction.

So:

• vidas la sunon brili = perception + object + infinitive
• vidas, ke la suno brilas = perception of a whole fact or event

Because Esperanto normally states the subject explicitly in each clause.

So the sentence has:

• subordinate clause: Kiam ni pasas tra la koridoro
• main clause: ni ĉiam vidas la sunon brili sur la muro

Even though the subject is the same in both clauses, Esperanto usually keeps it visible. Unlike some languages, Esperanto does not normally drop subject pronouns just because they were already mentioned.

So the repeated ni is natural and expected.

Because sur la muro describes location, not movement onto the wall.

• sur la muro = on the wall
• sur la muron = onto the wall

Here the idea is that the shining is visible on the wall. The wall is the place where the light appears, so the static form is used:

• sur la muro

This is the same basic contrast as:

• La libro estas sur la tablo = The book is on the table
• Mi metas la libron sur la tablon = I put the book onto the table

Yes. Esperanto word order is fairly flexible, especially with adverbs.

The version in the sentence:

• ni ĉiam vidas

is very natural and neutral.

You could also see:

• ĉiam ni vidas la sunon brili sur la muro
• ni vidas la sunon ĉiam brili sur la muro

But these may sound slightly different in emphasis.

As a general rule, placing ĉiam before the main verb is the safest and most natural choice for learners:

• ni ĉiam vidas

Because both are definite in context.

• la suno = the sun
• la muro = the wall

With something unique like the sun, Esperanto normally uses la, just as English does.

With la muro, the wall is understood as a specific wall in the situation being described, not just any wall.

So the article works much like English here.

No. It means that the sun's light is shining on the wall, or that we see the sunlight there.

This is similar to English, where we see the sun shining on the wall does not usually mean that the whole sun is somehow attached to the wall. It means the sun is casting light there.

Esperanto allows that same kind of expression naturally. The sentence is not meant literally in a physically impossible way.