Why is Friends so funny? I feel bored, and The Big Bang Theory has brought me the same feeling. . .

First of all, most of the humor in Friends is American humor, many of which are related to its language and culture itself, and many of which involve some natural associations with homophonic or implied meanings. If you only watch Chinese subtitles, you basically don't listen to the English conversations of the characters. Many jokes are incomprehensible, and some jokes are incomprehensible if you don't touch some American classic culture and popular culture.

Secondly, there are many gloomy adult jokes in Friends, which you may not understand on the first day.

The Big Bang Theory mainly mocks Sheldon's funny thinking and behavior. For example, they can't understand women and some seemingly normal things in society, and then their own logic and preferences are a bit weird to us. For example, they have a unique taste in clothes, and they worship people who are anime, toys and science fiction movies.

I hope it helps you. In short, you should think in English when watching American TV series, which is far from the punch line of domestic TV series.