It's coming along nicely, yes.
I like how Sirius forgot all about Lily because he was hungry! Typical teenage boy.
Very good with the exploding Grindylow!
Characterization for your intent is good, too, on the both of them.
This is off to a good start. To me, you've got the characterization going well so far. I look forward to more!
One thing, I think it's officially called "The Black Lake" instead of the "Great Lake"?