Which duolingo levels correspond with fluency levels (A1,A2,B1,B2,C1,C2) in a language? does anyone know?
There is no set standard as anyone can just plow through the courses while learning nothing and get to Level 25 by spamming Basics or some other simple skill.
The only way to determine that is by taking a test that is recognized worldwide that can also determine your level of fluency in a language.
HSK is one of the official examinations to test the certain level of proficiency. However, since anyone can possibly pass the examinations without thoroughly going over the characters, it does not clearly show how well they can speak or read. Few issues that concern improper proficiency-gauging:
1) There are in fact non-native speakers who can communicate outstandingly, but fail in the examinations.
2) The point of the exam is to determine whether or not you pass the exam. Thus, no grade points are included.
3) Some (sometimes, most) of the sections are easy to work out if one knows about 50% of the given Hanzis, which could possibly spell "rigged difficulty". The multiple choice problem section is the obvious that one can easily ace with minimal (or minimum) knowledge.
HSK and other related examinations are typically taken for entry and important situations, such as business, so don't rely on the exam studying tools too much. The best ways to learn Chinese are:
1) To develop your curiosity in learning and exploring different usages of Chinese in various of medias since style majorly plays the role in how depth is created, and how characters are used. I prefer this method since it helps me engage
2) Practice using Chinese since the action performed signals your brain in some way. For instance, if you practice writing, then your character-writing transmits some signals from your hand (or finger if typing) to your brain. The most inexpensive method is to change the interface languages to the target ones and practice! I did mine in several languages when I was playing games and using browsers.
In terms of the course structure, the closest level in European rank is close to higher A's but lower B's. As the blog mentioned, the vocabularies included are between HSK 1 and HSK 4. If that is not enough, learn more or brush up the learned lessons!