Cette trouvaille d’occasion est vraiment une bonne affaire !

Because trouvaille is a feminine singular noun.

French demonstratives change depending on gender and number:

• ce = masculine singular before most consonants
• cet = masculine singular before a vowel sound
• cette = feminine singular
• ces = plural

So:

• ce livre
• cet objet
• cette trouvaille
• ces livres

Since trouvaille is feminine, cette is the correct form.

Trouvaille is more than just a neutral find. It often suggests a good find, lucky find, or great discovery.

So in a shopping context, une trouvaille can mean something like:

• a great find
• a nice find
• a bargain find
• a gem you came across

It has a slightly enthusiastic feel. That matches the tone of the sentence well.

Here d’occasion is a fixed expression meaning second-hand or used.

In French, many noun phrases use de without an article to describe a category or type:

• une voiture de sport = a sports car
• des chaussures de randonnée = hiking shoes
• un livre d’histoire = a history book
• un objet d’occasion = a second-hand item

So trouvaille d’occasion means a second-hand find.

Also, de becomes d’ before a vowel, which is why you see the apostrophe:

• de + occasion → d’occasion

Not in this sentence.

French occasion can mean several things depending on context:

• an opportunity
• a chance
• in the expression d’occasion, second-hand / used

So although English occasion usually means an event or a special time, French occasion is broader. In d’occasion, it does not mean an event.

Because bon / bonne is one of the common French adjectives that usually comes before the noun.

Many French adjectives come after the noun, but some very common ones often come before, especially adjectives of size, beauty, age, goodness, and number. Bon / bonne belongs to that group.

So:

• une bonne affaire
• un bon livre
• une petite maison
• un vieux château

You would not normally say une affaire bonne here.

Une bonne affaire means a good deal or a bargain.

It does not literally mean a good business in this context. The noun affaire can mean several things in French, including:

• business
• matter/case
• deal/bargain

In shopping language, une bonne affaire is the natural expression for a bargain or something worth buying because the price is favorable.

In French, adverbs like vraiment often come after the conjugated verb.

So:

• est vraiment une bonne affaire

is the natural order.

Here, vraiment strengthens the whole idea: it really is a good deal.

English often allows more flexibility, but French usually prefers this kind of placement with a verb like être.

They are close, but not exactly the same.

• vraiment une bonne affaire = really a good deal
• une très bonne affaire = a very good deal

The difference is subtle:

• vraiment sounds like the speaker is confirming or emphasizing the truth of the statement
• très directly intensifies bonne

So:

• C’est vraiment une bonne affaire = It really is a good deal.
• C’est une très bonne affaire = It’s a very good deal.

Both are natural, but they highlight slightly different things.

Yes, absolutely.

• Cette trouvaille d’occasion est vraiment une bonne affaire !
• C’est vraiment une bonne affaire !

Both are correct.

The full sentence names the subject clearly: this second-hand find.
The shorter version with c’est is more natural when the object is already obvious from context.

So if you are pointing at something, C’est vraiment une bonne affaire ! would be very common.

A careful pronunciation is approximately:

Cette trouvaille d’occasion est vraiment une bonne affaire !
IPA: /sɛt tʁu.vaj d‿ɔ.ka.zjɔ̃ ɛ vʁɛ.mɑ̃ yn bɔn a.fɛʁ/

A rough English-friendly guide might be:

set troo-vy doka-zyon eh vreh-mon uhn bon ah-fair

A few useful points:

• cette sounds like set
• trouvaille ends with a -vaille sound, roughly like vai
• d’occasion has the French nasal sound in -sion
• est is pronounced eh
• the -s in est is silent
• bonne affaire flows smoothly because bonne ends in a pronounced n sound

You do not need to pronounce every written final consonant; French spelling often shows letters that are silent.