1. I would say "I have liked", as the verb "to like" is rarely used with the -ing ending. 2. I would say just "The Chinese think that 8 is a lucky number" because we don't have here any words that mark the need of using Present Perfect Continuous. 3. "The German" and "the German language" or just "German", the rest is correct. 4. I don't really understand what you wanted to say here, probably "It is interesting that in France people share drinks on the New Year's Eve"?

1. I have liked gelato for 5 years. 2. Chinese people think 8 is a lucky number. 3. The current German language has been spoken since the beginning/start of the century. 4. it's an interesting fact/thing about the French, they share drinks at home in/at the new year. are you trying to say only German people have spoken german since beginning of century, or the language has been spoken since the start of the century.

1) I have liked gelato for (the past) 5 years (The verb "like" is not a continuous verb (Ving) it's a statement verb) 2) Chinese think "8" is a lucky number (This is also a statement, a general fact. So present perfect cont. is a wrong tense) 3) Germans have been speaking the German language since the (start of the) first century. (You can use present perf cont. here) 4) An interesting thing about the people of the country of France is that they share drinks at home in the new year (there was a problem with the subject-verb agreement, this version is grammatically correct).

1. If you like gelato and have been enjoying it for the past five years, you would simply need to say, "I've been eating gelato for the past five years." That would automatically imply that you like it and that you've been eating it for five years. And that is how native speakers would convey it. 2. Chinese people think that 8 is a lucky number. 3. The German language has been spoken in Germany since the start of the first century. 4. The interesting thing about French people is that they share their drinks at home on New Year's Eve.