I invested Bitcoin in a fake site that was named as mega bit chain on the 6th of December. After that, I opened the site on the 12th of December; there was written: site is in maintenance. After two days the site was gone. Can I get my Bitcoin back?
If the website does not send them back to you, there is no way of getting your Bitcoins back. You may be able to sue them, but I am no legal advice. There is no authority that can reimburse you or transfer them to the scam website back to you.