What's wrong with this sentence 我终于快到中国了
我快到中国了。 I will arrive in China soon (O)
我终于到中国了。 I finally arrived in China (O)
我终于快到中国了。I finally arrive in China soon (?)
'finally' refers to the present or past events (you cannot say 'I finally arrive tomorrow'), while 'soon' referring to the upcoming events (future). These two words are conflicting with each other
Some said 我终于快到中国了 is understandable. In that case, 终于 would act as an exclamation (not adverb) --  &quot;我终于快到中国了&quot; could be interpreted as &quot;Finally, I will arrive in China soon!&quot;

does it need to be corrected?

To avoid confusion, you should change it to '我快到中国了' or '我终于到中国了'
If you really want to use 终于 as an exclamation, you should say  '我终于， 快到中国了'
There's another reason I don't like this sentence. It is like counting chickens before they hatch. Imagine, someone saying &quot;Finally, I am going to be promoted soon&quot; before he actually got the promotion, and ended up didn't get it?