Congratulations for making it this far! German is one of the hardest languages to learn as an adult. So give yourself a pad on the back. You ROCK! If you're signing up for German C1, then you've had a lot of German or have completed our German B2 classes. We will continue to follow the Goethe curriculum and you will have to purchase these two books:
Sicher! C1 Kursbuch: ISBN 978-3-19-001208-4
Sicher! C1 Arbeitsbuch mit CD-ROM: ISBN 978-3-19-011208-1
A good place to purchase these books is here:
Viel Spass und viel Erfolg!