They tell me that they will make me to learn German upto b1 in 2.5 months
closed as primarily opinion-based by IQV, Philipp, guidot, Björn Friedrich, Annatar Nov 14 '17 at 9:49
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Since nobody here knows your learning circumstances, if you work/study something else besides your german courses and who "they" are, its hard to tell if you can learn it in 2.5 months.
However the Goethe-Institut states that "candidates need to have completed between 350 and 650 45-minute units of teaching". So if you attend a full-time german course during this 2.5 months it may theoretically be possible to pass the exam successfully afterwards.