Just tried Dictation Beginner… it does get your brain working!
What I find difficult is hearing the rests, or silences, but I don’t know how to overcome that, other that by keeping at the Dictation Challenges every day… Good fun!
PS. I am profoundly deaf too, so that doesn’t help. I have an electronic keyboard and have output plugged into the implant in my head… like built in Karaoke Machine! 
I feel the sound more that hear it… but it works