Website is ok but i can access host account in siteground.com hacker told me that i have 24h time to pay 250$ please help me
You may report this to your hosting provider. Do you have backup of your website? If yes, change DNS of your domain name. I would suggest you that do not reply to hacker for a week. He would then think that you aren't serious about your website and will leave your website.
Send an email to Sitepoint support. Tell them that your account has been compromised and that the hacker is trying to extort you. They should be able to confirm your details and help you recover your account.