Hi Intet,
I started to learn Chinese 15 years ago - mainly spoken. Then through the years as my interest in China had grown I began memorising the Chinese logograms. Now, you mixed in the Koreans - They have their own written language, Hangul, which is the worlds most scientific written language. It was invented by King Sejong and his staff resposible for education of the Korean People. Classical Korean has many Chinese logograms but the modern Korean person has no need of using Chinese logograms, unless they are pursuing scholarly studies of literature. The two main dialects in China are Mandarin and Cantonese but there are other dialects as well.
You brought up my NGO work - Now, North Koreans use Hangul strictly without any Chinese logograms. This is in tune with the concept of "Juche" = self-sufficiency, as promulgated by Kim il-Sung. The North Koreans are trying to escape tyranny, so it is not immigration in the usual sense but the seeking of asylum and protection from a regime that only cares for its own survival.
My travels brought me first to East Asia then to Southeast Asia, ergo China, Japan, South Korea, Singapore, and Indonesia. I shall continue studying Chinese for the rest of my life. How many logograms that might entail? God only knows. If you have competency in, say, 5000 Chinese logograms you should then be able to look up whatever Chinese logogram based on the radical and the number of strokes in a Chinese dictionary.
No living human being today has memorised all the Chinese logograms, especially not all that are found in the Zhonghua Zihai with over 80,000 logograms, the reason being that those logograms are not used in daily conversation, nor in Government. Of course, in an advanced scholarly setting certain individuals might know the use of a certain logogram but it remains in the academic sphere. As an example of Classical Chinese logograms here is one:
http://bp3.blogger.com/_tMPW7Mr4XK0/RgBJ_azIh1I/AAAAAAAAAIE/vqEjLd4M0Ts/s1600-h/biang_2.gif
It has 57 strokes and denotes a special noodle dish found in Shaanxi Province. Phonetically, it is written as "biáng-biáng". Yes, there is a restaurant in a city(Xi'an) in Shaanxi Province that serves these noodles:
http://upload.wikimedia.org/wikipedia/en/8/8e/Biangbiang_noodles_The_noodles.jpg
According to a colleague and dear friend there is a restaurant franchise in Beijing called "Noodle King" which serves these noodles. I'm somewhat sceptical if they are any good. Once you take a regional food and mass-market it, it invariably will lose much because of mass-production techniques - (shave a little bit from here, take a little bit from there, add this spice or condiment here, take away that ingredient from there) well, you know what I mean.......
Yes, it is a delicious dish - the noodles are as thick as your belt and sometimes just as long.
I trust that I have answered your questions to your satisfaction?
Oh, I almost forgot - The Triads are from Hong Kong and they have their representatives in just about every country in the world.
Cheers,
CD