Can I get help, please?

I have this character and I don't know if it's going realistic and human, or it is just stupid. I'd love a second opinion and some advice.

Here's him:
His name is Thyssen, he's 17 years old, and born as a Blood Child (basically, he has a demon soul inside of him). He lost his whole family, except for his aunt Rose (he lives with her). He's been hiding he's a Blood Child or he could be took by the Goverment or by those demons or by one of the many satanic cults around.
Until, by accident, he has an encounter with a demon and starts to lose his mind because he's being possessed.

Sounds good or bad?
and excuse my grammar. I'm not english native and I'm still learning.

It sounds interesting. I think if written right, it could be really good! But about the loosing his mind thing, I think you should slowly build up to him going insane. And maybe instead of him just going crazy, maybe have him change a few things he normally did. For example, if he is really good at keeping his cool, he suddenly starts to have a short temper and things like that.

that's exactly what I was thinking. He became more and more violent. He's a violent character. And there's some moments where he gets completely possessed, and he becomes a kind of beat with superforce and telekinesis

First off, your English is wonderful. You've a better sense of English grammar than many of my American peers.

Also, your character premise is pretty good. I have some doubts on the name, 'Blood Child.' That just seems like more of a vampire thing. It's a rather…kitchy phrase.

I think any demon-related creature should have some sense of good and evil beyond human understanding. Say, he might be able to see a person's greatest flaw, or what sinful act they've done. Or even the value of their soul.

@Lord_Dunconius You're a genius

That sounds like a very interesting start! I agree with Celestial-B, if you write it well, it would make for a good story!

Thank you all!! I feel better now I'm heading well.

I have lots of ideas!

I think as long as you don't follow to many of the stereotypical features of an 'insane' character and think more logically when writing, it will turn out great :)