Verb conjugation of "stottern" in German

Of course I have already tried, but it did not work. I will try it again. Meanwhile, here is the reason for my short emails... only one hand free at a time, see explanation in the image of me.
My correction were added and highlighted with yellow markers and attached to this email. Tell me now if you have any questions about grammar rules, since I was a teacher 10 years ago.
I signed up at Vocabulix long time ago and I did not use the account, I even forgot it. But I am always remembering it when I receive newsletters or when I am contacted by other Vocabulix users.