I need to turn off the spell checker

How can I prevent my (German) texts from being corrected when I write them and having to delete the suggested correction every time so that this doesn’t happen? It is also wrong because in the line below the salutation it changes the first letter of the first word to a capital letter, although the sentence should continue in lower case. I have already deactivated everything in the Spell Checker settings, saved and restarted the client, but it doesn’t help, it stays as it was before, the word is always adjusted according to the correction suggestion. A little thing that is always annoying. What can I do, how can I deactivate it?

(What I did: eM Client Menu => Spell Checker => Unmark checkboxes => Save settings => restart eM Client)