How to know if you mastered a language

I learned multiple languages throughout my life and am actually adding another one (Russian) at this moment. Of course I learn languages because I find it fun, and it is very nice to be able to list more than 4 languages you can speak. But at the same time, it can be quite frustrating to get a certain fluency in these different languages.

The language this counts the most for in my case is Chinese. I have a Chinese face, which is kind of a double-edged sword. On the one hand, it is very convenient to be able to blend into streets in East-Asia and not have anyone question if I am a local or not. At the same time it places certain expectations on you that I cannot meet. Because I am a foreigner there. But nobody believes me.

When I was still studying Chinese, I started out speaking it very badly. I know that because I was reminded of it everytime I talked to locals. Even more so since I hung out with Dutch-Chinese friends who spoke Wenzhounese or Cantonese at home and thus sounded a lot more natural. New friends even told me that they could not really understand me for the first 6 months in Chinese, but somehow everything had worked out fine.

Generally, my conversations would go something like:

Q: Can you tell me where the subway station is?
A: ThesubwaystationisoverthereandyoujustgonorththenturnleftandarriveatentranceA.
Q: Sorry, can you repeat?
A: Howcomeyoucannotunderstand? WhyisyourChinesesobad?
Q: I am not Chinese, can you talk a bit slower?
A: YouarenotChinese? ButyoulookChinese!
Q: Please, just tell me where the subway station is.
A: Go north. Then turn left.

For most ‘general’ foreigners, the conversation goes something like:

Q: Ni hao, can you tell me where the subway station is?
A: Oh my! Your Chinese is so good! The subway station is north and then turn left.

Quite a difference and it caused me to be pretty frustrated while learning Chinese. Now that I am more fluent, in a foreign environment and not expected to speak Chinese, I get the opposite. After all these years people sudenly start complimenting me. Saying that for a foreigner (the keyword of course) my Chinese is very good. And I always think to myself: “TOO LATE, I WILL NOT ACCEPT YOUR COMPLIMENT. SHOULD HAVE SAID THAT ABOUT 10 YEARS EARLIER.” Plus, now it makes me question my level of Chinese. Is it only good because they know I am a foreigner? Do I now also have the ‘benefit’ of foreigner bias?

I guess it is asking yourself these questions that shows you have some proficiency.