If you are taking a class using Netzwerk , stick to it. Switching workbooks mid-course will confuse you because the vocabulary pacing is different.
Many Goethe-Instituts and university libraries offer a "digital lending" service. You can log in with your library card and download a time-limited PDF (usually 24 to 48 hours) legally. Netzwerk B1.1 Arbeitsbuch Pdf