Use "Nominalstil" (noun-heavy style) common in German higher education.
Here is the direct link to the official (word list) PDF from the Goethe-Institut: i goethe zertifikat c1 wortliste pdf link
However, you can still find official prep materials and highly reliable thematic lists to bridge the gap. Here is everything you need to build your C1 word bank. 1. Official Goethe-Institut Resources Use "Nominalstil" (noun-heavy style) common in German higher