I think "have been" is used very commonly in English, but I'm not sure when I can use it.

It's not as common as it used to be, but many people in Asia still prefer to live with their parents even after they're grown up. Is it common for western people to live with their parents as well?

In previous decades, it was common for people to move out to live on their own once they graduated. People became independent in their early 20s. Now, it is more common to live with your parents longer as it is very expensive to live on your own or to buy/rent your own home. However, it is likely still not as common as it is in countries in Asia. Ex: I moved out when I graduated university. Ex: I lived with my parents until I got married.

What is "311 CD"?

"311" is the name of an American rock band, so he is saying he purchased "311's" new CD.

Is "got to" exactly same as "have to"?

"Got to" is a more informal, slang version of "have to", unless you say "have got to", which is still a bit informal. The meaning of both of these expressions is very similar as they mean that someone needs to do something, however, "have to" often implies that it was someone else's decision for something to be done or someone must do something because they were forced by someone else. Ex: I have to be home before dinner or else my mom will be mad. Ex: You have to go to school. "Got to" usually expresses more of an obligation or guilt by that person to do something. In a positive context it can be used to mean that someone needs to do something, but unlike "have to" it does not imply that they are forced. Ex: I don't want to go to the party but I've got to. Ex: You've got to try this food!

What's "sell into" mean and when's it used?

"Sell into" means to give or hand over something, or someone in relation to slavery, to enter a specific situation for the exchange of goods or money. It's mostly used in relation to shares and bonds now! Ex: Most banks prefer to sell into a stable market. => selling shares or bonds Ex: They sold their products into the primary market for a higher value.

What is the role of "a couple of" here? How different are "break a couple of rules" and "break rules"?

"A couple" means more than two, or a few. When used in this context, it works to add a rough estimate of numbers: a couple, a few. The speaker has used "broke a couple of rules" to add a feeling of casualness to the statement. "Break rules" sounds a bit too stiff, so using a number-related expression like "a couple," "a few," or "some" can be used to make the sentence flow more smoothly and sound more natural. Ex: Let's buy a couple bottles of wine and stay in tonight. Ex: I have a couple errands to run today, so I won't have time to hang out with you.