The B1 level introduces complex grammar:

If you cannot find a single arbeitsbuch+b1+pdf+free that works, build your own using modular resources. This is often better because you target your weak spots.

An Arbeitsbuch, also known as a workbook, is a supplementary book used in language learning to provide additional practice and exercises for learners. It typically includes grammar and vocabulary exercises, reading and listening comprehension, and sometimes writing and speaking activities.