While I like your variety of voices in this current demo, you don't need to say exactly what role you're attempting to do every single time, as it unnecessarily extends the demo reel's length(which to a considerable amount of people, can end up being generally exhausting to get through). Just leave the audience themselves to guess what exactly they're listening to the next time you make a demo reel, and I guarantee that you'll have the chance of seeing more users willing to leave a critique on your work.
And this is a personal quibble of mine, but I feel adding some more enthusiasm into your various performances(when appropriate), will help make the characters feel that much more alive and interesting to listen to, for many people.
But for a first attempt, this was quite good. And on the bright side, you can only get better from here.