The B2 exam goes for up to 3,5 hours. This time includes a 2,5-hours-long written part and an hour-long speaking part. Please see the table below for details (note also that you will only have 30 minutes to prepare to the delf b2 interview).
If you can organize yourself without outside assistance, then the textbook is all you need to prepare for delf b2 well. Speaking from personal experience, I can say that it make you 100% ready for the listening and reading parts. You will: 2b1af7f3a8