In my post How much German do you need in Germany? I have been talking about two main groups of learners of German amongst international students in Germany: Those who want to study in an English study program and those who want to study in a German study program.
For the first group I recommended to acquire at least basic German skills for survival in Germany’s everyday life, for the others I explained that they’ll need a German language exam like DSH or TestDaF to get an admission to the university.
For “survival German” I supposed the level B1 of CEFR and for the German language exams for university admission the level C1. So now I come to answer the question in the title of this post: How long will it take you (in Germany) to reach your desired level of German?
As you might know the answer to this questions is depending on many individual factors like your experience in language learning, your ability to motivate yourself for language learning, how much time you spend on studying, and so on. So you’ll understand, that I can only talk about an average student.
I usually calculate between 150 (fast learner) and 200 lessons (average learner) per level of the CEFR. As B1 is the third level of the CEFR, that means between 450 (fast) and 600 (average) to reach B1. As C1 is the fifth level of the CEFR, it makes between 750 (fast) and 1000 (average) to reach C1.
If you take an intensive course in Germany with 25 lessons per week (=ca. 100 lessons per month) and you start from zero, you’ll find, that it lasts between 4,5 and 6 months to finish B1 resp. between 7,5 and 10 months for C1.
If you finished German courses in your home country, you’ll achieve your goal even faster, but according to my experience you usually should calculate your level in Germany one level lower than the level in your country.