You can update the theme via FTP by overwrite the existing one.
- Download the latest version from themeforest
- Unzip the exquisite.zip file
- Connect to your server via FTP
- Upload the extracted exquisite folder to /wp-content/themes on your server and overwrite the existing files.
Note: All your modifications in the code will be lost so we recommend to use a child theme if you want to edit the code. You can learn more about child themes here.