So interesting! Harry being enrolled in another school is certainly a novel way to get Harry selected as a champion. 

I'm interested to see where Harry is placed year wise and how strong his knowledge is in each subject. I bet he scores extremely low in history.

Hogwarts was Harry's "home." I wonder how he feels about leaving it, even though everyone seemed hostile to him after he was selected as a champion.

it seems that Harry is getting a lot of information all at once. He is most likely overwhelmed. And the Headmistresses should probably try to explain things very succinctly. For example, she gave a very long list of all the creatures. That should probably have been summarized. She seems more in tune with Harry's needs, so I think she would also be in tune with not overwhelming him with information.

The Headmistress seems slightly overpowered by having three creatures in her, including a witch. Having her display a forceful personality more at Dumbledore and keeping her heritage a secret would have probably made the story flow faster and fleshed her out more. More descriptions of her mannerisms and movements, body language, and tone need to be provided. Harry's too.

Who is paying for Harry's things? Is he going to pay the Headmistress back, or is the school buying and paying for everything? 

When Harry goes to the school and gets new textbooks, will they be in English or Russian? Will he understand his teachers and classmates if they only speak Russian in class?

Why is Harry allowed to go to the Russian school when all the other champions from other schools are at Hogwarts?

How is Snape going to come back into the story?

Does Harry have his broom with him? It wasn't mentioned with his trunk and owl cage.

Thanks for writing and sharing this story. I look forward to reading more when it is updated.