Rule of thumb, always made regular backups of your theme, files and database so that you can gracefully roll back if you run into issues. In your case, make an new backup, log into your server via FTP and delete the Avada folder via /wp-content/theme/, or, deactivate Avada in the WordPress Dashboard >> Appearance >> Theme section and delete it there.
Once that is done, re-upload the current version you are running (do not overwrite previous theme files). If you need/want to customize facets of the theme, use a child theme and the appropriate Avada/Fusion Builder hooks. This ensures that changes are implemented correctly and will be update safe moving forward.
Thank you kindly