The DELF B2 requires a good level of language competence which is tested within a rigorous framework. Moreover, it requires a fairly good knowledge of cultural and social French matters. In addition, you are expected to understand the way French people submit an exam, which can be very different from what you are used to in your own country.
If you have already passed the DELF B1, you may have a fairly good knowledge of the exam strategies, but there is a substantial difference between B1 and B2. As a matter of fact, the candidate has a degree of fluency and spontaneity in interactions and is capable of correcting his own mistakes. Nonetheless, we still find the four language proficiencies of reading, writing, listening and speaking, each worth 25 marks of the 100 total marks. You need to score 50 marks to achieve a pass grade and a minimum of 5 out of 25 in each paper.