First of all, you need to change the passwords for all users and change their roles from administrator to lower-level ones. Only your main user should have the administrator role. This can help if it was a brute-force attack.
I opened your page and saw that it displays the error message, “There has been a critical error on this website.” You need to check the link to the troubleshooting article below the error message. Try following the steps from the article and come back with more specific information. I will try to help you.
