> China has bought Tibet from the British

China invaded and annexed Tibet in 1951 [1].

You may be thinking of Hong Kong, which the British invaded and annexed from the Qing dynasty [2] and then handed back to China in 1997 [3] under conditions that Beijing defaulted on in 2019 [4].

> what have they done with Taiwan?

Same as America has been doing with Greenland.

[1] https://en.wikipedia.org/wiki/Annexation_of_Tibet_by_the_Peo...

[2] https://en.wikipedia.org/wiki/History_of_Hong_Kong

[3] https://en.wikipedia.org/wiki/Handover_of_Hong_Kong

[4] https://en.wikipedia.org/wiki/2019%E2%80%932020_Hong_Kong_pr...