My iPhone is hacked

I think that my iphone is being hacked,

I received an email yesterday from my own gmail account claiming that he is seeing me from my camera and he installed trojan in my device, therefore he claims that if I didn’t send the money to him through bitcon he will transfer the email to everyone.

furthermore, today when I was trying to open my Twitter account, someone was trying to sign in and I changed my password quickly . And now they’re trying to enter through my apple ID too ! What should I do? And how could I protect my iphone now?