Hey, I honestly don't know if this is just a terrible implementation or a bug.
The note and spellchecking is obviously in German, but I don't think that this has any impact on the result.
The first screenshot shows a right-click on a wrong word ( either the "e" at the end is to much or its missing an "n"). The choices are good and its fine that I can add it to a custom dictionary ( "Zum Wörterbuch hinzufügen" in German).
The second screenshot is a Problem:
It shows a right-click on a word that is correct, but so uncommon ( its a compound word) that it has no dictionary entry. This is fine. BUT why in the ***** world cant I add this ( or any other word I like) to the dictionary ???