In the next five months I will be having a lot of free time. If not considering some perturbations and problems, there is an ideal period of time in order to improve my language skills considerably. I consider myself to be B2-C1 level in German and B2-B1 level in English. My productive skills in both languages are not at a high level, but my understanding in both languages is really proficient, I think, because I can read non-fiction and science textbooks and understand popular-science podcasts in both languages. When it comes to speaking, I rarely practiced it, and I will not have so much opportunity to practice it in the future, but I think it is not a big problem anymore because I also can improve my speaking skills to a certain extent through writing. So, I will be mostly practicing my languages through reading, listening, and writing. And I think that is a good way to improve my language skills in both languages. I hope to achieve C2 level in German and C1 level in English. That is an ambitious goal, but if I take into consideration the considerable amount of free time and my big interest in both languages, I think that it is achievable.
Question: How do you plan on achieving those milestones? Are there for example specific books you have in mind, or is there a specific learning and exercicing path you are considering?
Do notice that C2 really means understanding everything without any noticeable effort, and communicating (actively, i.e. speaking and writing) at a very precise and nuanced style.
I have found out today that the period of time will be shorter. I was enthusiastic at first but now I see that everything seems pretty unrealistic, but I still can improve my language skills considerably. I am planning to read books and articles und summarize them in the written and in the spoken word. I also want to continue listening to popular-science podcasts in both languages. That is pretty much what I want to do. However I understand that this is a lifelong journey and that my enthusiasm at first made me believe an unrealistic thing for some minutes, but I still can improve my languages.:)
I didn't mean my comment to be discouraging. As you know from previous posts, I estimated your current German level to be around C1 (which is darn high), so reaching that level in a Certificate in a short amount of time is definitely realistic, in my opinion. But who am I to judge, from your point of view I am just a random guy form the Internet (who happens to have read and corrected some of your texts, yes, but still). It was also meant as a reminder that C2 is really a very high level to achieve. For instance, I don't think that "just" reading non-fiction is enough as "preparation", because there I miss at least two different aspects: 1) the variety of language you're exposed to (in terms of content, style, grammar structures, vocabulary, idioms, etc.), and 2) the active part of speaking and writing and communicating, under the expected constraints like being quick and precise enough so it feels "natural". All of these comments are not meant to cause distress, only to provide a (subjective) sense of perspective and reality. But in the end, it's up to you to reflect on it and try things out.
And also from a mathematical point of view - I am still a nerd, "sorry" -, I think people should not forget that jumping from C1 to C2 involves at least the same amount of work required to reach C1 in the first place. After A2, each consecutive level is an exponential growth in terms of required effort. It's definitely not linear. You can see this for example in terms of vocabulary, where realistically C1 is like 8.000 words (lemmas) and C2 is 16.000 at the very least.
Next to this, the path to the upper levels requires a huge amount of grinding without following a standarized path like "learn this and this stuff about grammar" and "here are some vocabulary lists for cramming". So it's more like exposing yourself to the "big open world" rather than following a rather boringly beaten track, which is what A1-B2 is, in my opinion
No, I didn't mean that your comment was discouraging; I rather realized myself that it is pretty unrealistic ( I mean reaching the C2 level). I like your way of pointing out the fact that achieving a high level in a language is all about exposing yourself to "the big open world" rather than following a boring track, because I don't want to sit at the table with a textbook and do exercises anymore; I'd rather consume language and learn something through languages, like maybe learning biology and watching lectures and reading books about it in my languages.