Je voudrais quelques renseignements sur ce service, madame.

Voudrais is the present conditional form of vouloir for je.

• infinitive: vouloir = to want
• conditional stem: voudr-
• ending for je: -ais

So je voudrais literally means something like I would want, but in normal English it is best understood as I would like.

In French, renseignement often refers to a piece of practical information or a detail, so when someone is asking generally for information, the plural renseignements is very common.

• un renseignement = one piece of information / one detail
• des renseignements or quelques renseignements = some information / some details

So French often treats this idea as several pieces of information rather than one mass noun.

Both can mean information, but they are not always used in exactly the same way.

Renseignements often suggests:

• practical details
• information you ask for from a person or office
• customer-service or administrative information

Informations is broader and more general. It can be used for news, facts, or information in a wide sense.

In this sentence, quelques renseignements sur ce service sounds very natural because the speaker is asking for practical details about the service.

Yes. In French, sur can mean about or regarding when introducing a topic.

So:

• des renseignements sur ce service = information about this service

Other possible expressions are:

• à propos de ce service
• au sujet de ce service
• concernant ce service

But sur ce service is simple, common, and natural.

Because service is a masculine singular noun that begins with a consonant sound.

French demonstratives work like this:

• ce
  • masculine singular noun beginning with a consonant: ce service
• cet
  • masculine singular noun beginning with a vowel or mute h: cet hôtel
• cette
  • feminine singular noun: cette idée
• ces
  • plural noun: ces services

So service takes ce.

There is no article because quelques already acts as the determiner.

So:

• quelques renseignements = some / a few details
• des renseignements = some information / some details

Both are possible. The version with quelques can sound a little more modest or specific, as if the speaker is asking for a few details rather than speaking more generally.

Madame is a form of direct address. The speaker is addressing the woman politely, like madam or ma’am in English.

The comma is used because it is separate from the main sentence:

• Je voudrais quelques renseignements sur ce service, madame.

You could also place it at the beginning:

• Madame, je voudrais quelques renseignements sur ce service.

In the middle of a normal sentence, madame is not usually capitalized. It is capitalized in some formal contexts, especially at the start of a letter: Madame,

It is polite, standard, and very usable in real life. You could say it:

• in a shop
• at a hotel desk
• in an office
• on the phone
• when speaking to customer service

It is formal enough to be respectful, but not so formal that it sounds unnatural. If you want to make it even softer, you could add s’il vous plaît:

• Je voudrais quelques renseignements sur ce service, s’il vous plaît.

Yes. J’aimerais is also very common and polite.

• Je voudrais quelques renseignements...
• J’aimerais quelques renseignements...
• J’aimerais avoir quelques renseignements...

All of these are natural. Je voudrais is a very standard request formula, while j’aimerais can sound slightly softer or more personal.

A careful pronunciation is approximately:

Je voudrais quelques renseignements sur ce service, madame.
/ʒə vu.dʁɛ kɛlk ʁɑ̃.sɛɲ.mɑ̃ syʁ sə sɛʁ.vis ma.dam/

A few useful points:

• je is often pronounced with a very light vowel
• voudrais sounds roughly like voo-dreh
• quelques is short; the final s is silent
• renseignements contains nasal sounds, which are difficult for English speakers
• madame is pronounced clearly as ma-dam, with the final m heard

If you are learning pronunciation, the hardest word here is usually renseignements.