If you're looking for a thorough and reliable grammar review resource for the B1 level, I highly recommend the Grammatik B1 PDF. It's an excellent addition to any German language learner's study routine.
A structured grammar book or PDF allows you to: grammatik b1 pdf
While there are many files floating around the internet, we recommend sticking to trusted sources to ensure the German is correct and up-to-date. Here are the gold standards for B1 grammar: If you're looking for a thorough and reliable