So a guy said he's skining me in Fortnite and I gave him my account details and he changed email and password. Now my question can I ask him Legal?
In their own stupidity no law works.
You do not soiso (I guess you're under 18 … Rarely seen someone stupider)
And since you gave him the data "volunteer" you can't do anything there.
It's like volunteering to give your purse to a stranger on the street and then wondering why this person is running away with it.
And what do you want to do about it? He did not steal the data, you gave it to him voluntarily.
and that's why it's online EVERYWHERE! And that since I was little (I'm now 24) that you pass passwords etc not even to friends because that's what happens! No matter what game, which side, etc.