This is fabulous! If yours had 0 accidents at 8 weeks old today, that's 3 less than my 14 week old had today! Mine is smart, but of the 5 puppies I have raised, house training will be the worst with this one. And you are seeing all the smart learning these Dobermans do!
Maybe you are inexperienced, but you are doing a lot correctly! Like
@MichiH suggested, though, really work on the resting as a skill to be trained, and make his crate only big enough for him! He will be the best big boy in no time, there will be great days and some not great along the way. Today is a not great day for us in my house, but I know tomorrow is just around the corner.