qetadg wrote: Now, the problem is that Cantonese Chinese does also exist. From what country should I watch drama in order to hear Mandarin Chinese? Thank you in advance
You could watch Prince of Lan Ling. The female lead (Ariel Lin) is taiwanese and if I didn't remember wrongly, she was not dubbed so she had a taiwanese accent while the rest of the characters spoke China's mandarin. (I'm not 100% sure though, someone correct me if I'm wrong. I just had this impression because I remember thinking that Ariel's mandarin was pretty jarring while watching that drama.)
There's also a recent chinese drama called Nervous, where the male lead is taiwanese and the rest are from the mainland. You can clearly hear how his accent is different from the rest.
Also there's the Beijing/standard mandarin accent, which has the famous 儿 sound (something like "er", 点儿,照片儿 dian'er, zhaopian'er etc etc), which they only have in northern China. In other places in the south, like Shanghai, they speak faster but some people find it easier to understand than the Beijing accent.