The Centrum voor Levende Talen (CLT) in Leuven, Belgium offers two types of German language courses: (1) for native speakers of Dutch, Afrikaans, Danish, Norwegian or Swedish and (2) for native speakers of other languages. The first category of learners can follow the "fast track", with 70 (classroom) hours per course, up to level B1. The other category of learners follows the "standard track" with 120 hours per course up to level A2, after which the fast track and the standard track are "merged".
Assuming that English being in group 2 is not an oversight, you need the following courses to reach level B2 at CLT:
- a year-long course with 120 hours to reach level A1;
- another year-long course with 120 hours to reach level A2;
- four semester courses of 70 hours each to reach level B1;
- two year-long courses of 120 hours each to reach level B2.
Starting from level A2, you would need to take 520 hours of classes (4 * 70 + 2 * 120) at CLT to reach level B2. Of course, you would also need to study a bit at home to keep up during the semester and to pass the exams at the end of each semester. Let's assume that 1 hour of study per week would be sufficient; this is usually sufficient to pass the tests at CLT though not necessarily sufficient for top marks. Since the year-long courses have 30 weeks (ignoring holidays) and the semester courses have 17 or 18 weeks, you would need to add roughly 100 hours (in total) of private study to the classroom hours. That would result in 620 hours of study to move from A2 to B2.
The Goethe-Institut assumes that you need between 600 and 800 classroom hours (1 classroom hour = 45 minutes) to pass the B2 exam; my estimate based on the CLT courses is within that range. In order to fit this into a single year (365 days), you would need to study at least 80 minutes per day; if you have only nine months left (at the time of writing, the question is three months old), you would need to study roughly 135 minutes per day. Note that this excludes the time you spend on looking for learning materials etc.. Language classes in the target language give you a lot of comprehensible input, i.e. input that is adapted to the level you have. When you are learning on your own, you will need to find that input on your own, which can be time-consuming unless you find a series of books that are appropriate for autonomous study. (Many books for classroom use are not appropriate for autonomous study.) Even if you find good textbooks with CDs, you will still need to find additional audio materials (or get a second series of textbooks) to get enough audio input. You will also need to find someone to practise your oral skills with.
The Goethe Institute's B2 exam is being reworked into a more modular form that will become available in January 2019. This modular exam will consist of four parts: reading (65 minutes), writing (75 minutes), listening (ca. 40 minutes) and speaking (15 minutes). The Goethe Insitute provides some practice materials, both for the new B2 exam and for the current (until end of 2018) exam, but it does not recommend specific textbooks or study materials. However, you can practise your German for free on the website section Kostenlos Deutsch üben.
Of course, many publishers have noticed that there is a market for books that help you prepare for language tests. For example,
And this is just a selection from German publishers. There are also similar books by publishers in other countries. The above books contains practice exams and/or tasks similar to those in the Goethe Institute's exams; in other words, they help you become familiar with the exam format but they do are not intended as course books to help you reach level B2. These books don't replace regular textbooks, they are only really useful to learners preparing for this specific language test. These books typically also contain tips on how to tackle the individual tasks that make up each section of the exam.
For regular textbooks, you need to look elsewhere, e.g., from the same publishers as above:
Again, there are also many other series and titles by publishers outside Germany.