I want to ask why my account has been banned?

Your were banned from using this site.
Either your referrer or you created multiple accounts and once any of you get caught, they ban all the linked accounts with the main account that cheated them. You will need to tell them about this and if you are not guilty, they will restore your account like they did in my case. My referrer was found guilty in that case and they banned all the linked accounts, but they saw my history and decided to restore my account as I have never cheated any websites before and will never do that.