Transfer from the airport Charles de Gaulle

Of course there are buses, as well as trains.

Uber is not allowed at the airport. You can take a taxi for a set price (53 or 58€) depending where your hotel is located. Only use taxis from the official taxi ranks. Ignore anyone who approaches you offering a taxi - they want to scam you. See this site:

https://www.parisaeroport.fr/en/passengers/access/paris-charles-de-gaulle/taxi

You can also take the RER into the city for about 12€. See this site:

https://www.parisaeroport.fr/en/passengers/access/paris-charles-de-gaulle/public-transport/rer-b

Your hotel should be able to give you the best directions.

All kinds of options: train, bus, taxi are the most common. More info here: https://www.parisaeroport.fr/en/passengers/access/paris-charles-de-gaulle

If traveling alone, RER B for 10.30 into the city and to wherever you are staying in the city is the way to go. The ticket will take you from CDG to Paris and there you can transfer to the metro to get where you need to go.

You have the choice of the taxi if you are willing to pay for that piece of luxury, or take public transport, ie the RER similar to a light rail train. There is also the Air France bus, which goes from GDC to the Opera house. The RER goes directly to Gare du Nord station in Paris.. After that you have the option of a taxi, the bus or the Metro, all of which you catch at Nord.

The Air France buses ceased service a couple of years ago. The bus to the Opera is run by the Paris region transportation service, RATP.

The RER B stops at additional stations within Paris: Châtelet-Les Halles, St. Michel, Luxembourg, Port Royal, Denfert-Rochereau, and Cité Universitaire.
One could be closer to your destination or have better connecting bus or metro lines.

"city centre" is a very vague term. Tell us specifically where you want to end up and maybe you will get more specific info. Taxis in general are the simplest and most costly. Train/RER can be complicated for a first time visitor (with changes and stairs), but is often the cheapest option. Über can be okay, but not necessarily the fastest or most available (they can't go in the lanes set aside for taxis and buses). Plus their fares vary based on demand—unlike taxis, buses and trains. I personally usually end up near Gare Saint Lazare, so the RoissyBus is a very good, simple and cheap option for me. But again, it depends on where you want to go.

Thank You:)

"Uber is not allowed at the airport."
Uber is allowed at the airport. It is just not the necessarily the best way to get from CDG to Paris because Uber drivers are not allowed in the taxi line and thus one has to figure out how to connect with the Uber driver.

Just be aware that the RER B (the train) has several weekend closures coming up, as well as late at night. There is connecting bus service to another point to catch the train into town but it is a hassle.

It feels like you don't have Rick's book, he covers the various options pretty completely