Can anyone tell me why Tibet wants to be independent from China?
Basically you have answered your own question. Tibetans are not Chinese, but a seperate country with a different culture. Once a warlike people with a huge empire covering much of central Asia (including large parts of China!), they were invaded by the communists under Mao in 1951. The monasteries were systematically destroyed, and the monks and nuns abused, tortured and often executed. The population were forcibly indoctrinated with political dogma, with unreserved brutality, and some estimates put the death toll since 1959 at over 10%. It is to the great shame of the rest of the world that this occupation by China continues to this day.