La nouvelle locataire parle avec la propriétaire dans l'agence immobilière.

La means we are talking about a specific, identifiable person: the new tenant.

If you said une nouvelle locataire, it would mean a new tenant, introducing her as not yet specifically identified.

So the choice between la and une works a lot like the vs a/an in English.

In French, some adjectives often come before the noun, and nouveau / nouvelle is one of them.

So:

• une nouvelle locataire = a new tenant
• un nouveau locataire = a new male tenant

Many French adjectives come after the noun, but common adjectives like nouveau, jeune, petit, grand, and vieux often come before.

Because locataire is feminine here: la locataire.

French adjectives must agree with the noun they describe in gender and number:

• masculine singular: nouveau locataire
• feminine singular: nouvelle locataire
• masculine plural: nouveaux locataires
• feminine plural: nouvelles locataires

So nouvelle matches the feminine noun phrase la locataire.

Some French nouns have the same form for masculine and feminine. Locataire is one of them.

So you get:

• le locataire = the male tenant
• la locataire = the female tenant

The gender is shown by the article and by any agreeing adjectives, not by changing the noun itself.

Literally, propriétaire means owner or property owner.

In a housing context, la propriétaire usually means the female owner/landlady.

Like locataire, propriétaire often keeps the same form for masculine and feminine:

• le propriétaire = the male owner/landlord
• la propriétaire = the female owner/landlady

So the article tells you the gender.

Because agence starts with a vowel sound.

In French, le and la usually become l' before a vowel or silent h:

• la agence → l'agence
• le hôtel → l'hôtel

This is called elision, and it makes pronunciation smoother.

Because most descriptive adjectives in French come after the noun.

So:

• agence immobilière = real estate agency

That is the normal order. English often puts adjectives before the noun, but French often puts them after.

Because immobilière agrees with agence, which is feminine singular.

Compare:

• un agent immobilier = a male real estate agent
• une agente immobilière = a female real estate agent
• une agence immobilière = a real estate agency

So the adjective changes to match the noun it describes.

Both can be possible, but they suggest slightly different things.

• parler avec quelqu’un = to speak with someone, to have a conversation
• parler à quelqu’un = to speak to someone

Here, avec emphasizes that the two people are talking together.

Dans emphasizes being inside the place physically.

So:

• dans l'agence immobilière = inside the real estate agency
• à l'agence immobilière = at the real estate agency, more generally

In this sentence, dans gives a more concrete picture of where the conversation is happening.

A rough English-style pronunciation is:

lah noo-VELL loh-kah-TAIR parl ah-VEK lah proh-pree-ay-TAIR dahn lah-ZHAHNS ee-moh-bee-lee-AIR

A few useful points:

• the final -t in locataire is silent
• the final -s in dans is silent
• l'agence flows together smoothly because of the elision
• immobilière has a stressed-sounding final part like -lee-air

As usual, the English-style approximation only helps a little; the real French sounds are slightly different.

Here are the main possibilities:

• Le nouveau locataire parle avec le propriétaire dans l'agence immobilière.
  = The new male tenant is speaking with the male owner/landlord in the real estate agency.

• La nouvelle locataire parle avec le propriétaire dans l'agence immobilière.
  = The new female tenant is speaking with the male owner/landlord in the real estate agency.

• Le nouveau locataire parle avec la propriétaire dans l'agence immobilière.
  = The new male tenant is speaking with the female owner/landlady in the real estate agency.

So the articles and some adjective forms change, but the overall sentence pattern stays the same.