L’architecte dit que le salon sera plus clair si nous déplaçons le miroir.

Because architecte begins with a vowel sound, so the article contracts:

• le architecte → l’architecte
• la architecte → l’architecte

French does this before most vowel sounds and mute h.

Also, architecte can refer to a man or a woman. In this sentence, l’architecte does not tell you the gender by itself.

Usually no. In everyday French, le salon most often means the living room or the lounge.

So although the word looks like English salon, its everyday meaning in this context is a room in a house, not a hair salon or beauty salon.

Dire means to say or to tell, and que introduces the clause that follows:

• L’architecte dit = The architect says
• que le salon sera plus clair = that the living room will be brighter

So que here means that.

In English, that is often optional:

• The architect says the living room will be brighter
• The architect says that the living room will be brighter

In French, que is normally required.

Sera is the simple future of être:

• je serai
• tu seras
• il/elle/on sera
• nous serons
• vous serez
• ils/elles seront

So le salon sera plus clair means the living room will be brighter.

French uses the future here because it refers to a result in the future.

Here plus clair means brighter or lighter.

• clair can mean light, bright, or clear, depending on context.
• With a room, plus clair usually means it will have more light or seem lighter.

So this is probably about the room feeling brighter because of the mirror.

After si meaning if, French normally uses the present tense, not the future, when talking about a real possible condition.

So French says:

• si nous déplaçons le miroir = if we move the mirror

not:

• si nous déplacerons le miroir ❌

This is a very important pattern:

• Si + present, future
• Si nous déplaçons le miroir, le salon sera plus clair.

It works a lot like English:

• If we move the mirror, the living room will be brighter.

Because after si in this kind of conditional sentence, French uses the present tense in the if-clause, even when the meaning is future.

Structure:

• si + present
• main clause in the future

So:

• si nous déplaçons le miroir = if we move the mirror
• le salon sera plus clair = the living room will be brighter

This is normal French grammar, not a special exception for this verb.

The verb is déplacer. In the nous form of the present tense, it becomes nous déplaçons with ç.

This is done to keep the soft s sound of c before o:

• je déplace
• tu déplaces
• il déplace
• nous déplaçons
• vous déplacez
• ils déplacent

Without the cedilla, c before o would sound hard, like k, which would be wrong.

Both are possible, but they feel a little different.

• nous déplaçons = more standard/formal
• on déplace or more naturally si on déplace le miroir = more everyday spoken French

So this sentence sounds correct and fairly standard. A spoken version might often be:

• L’architecte dit que le salon sera plus clair si on déplace le miroir.

In French, nouns usually need an article or determiner:

• le miroir = the mirror
• un miroir = a mirror
• ce miroir = this mirror

So déplaçons le miroir is the normal way to say move the mirror.

French uses articles more consistently than English does.

The sentence is built like this:

• L’architecte dit
  subject + verb

• que le salon sera plus clair
  que

  • subject + future verb + comparative adjective

• si nous déplaçons le miroir
  if

  • subject + verb + object

So the full structure is:

[The architect says] [that the living room will be brighter] [if we move the mirror].

French word order here is quite close to English.

The original sentence is already natural. But in everyday speech, a French speaker might say:

• L’architecte dit que le salon sera plus lumineux si on déplace le miroir.
• L’architecte dit que le salon sera plus clair si on bouge le miroir.

A few notes:

• plus lumineux can sound slightly more specifically about light
• on is very common in speech instead of nous
• bouger is a common everyday verb for move

But your original sentence is perfectly good French.