German power words do not recognize the grammar

Hi, I have visited your power word list, and selected the word “festlich” (“festive”) for my blog post.
However, since German uses a lot of different writings based on the German grammar, RankMath did not recognize the word I had to use, “Festlicher” 🙁
So, while in English you can always use “festive” (“festive roast”, “festive house”, “festive party”), in German you have to write “festlicher Braten”, “festliches Haus”, “festliche Party”.
Do you have a solution for this?
// Juergen