I’m sorry to read that.
First and foremost, please check the WordPress prerequisites here:
For better performance and improve security, we obviously recommend PHP 7.4+. Nevertheless, if this is not possible for you (server type, incompatibilities with plugins, etc.), we recommend at least version 5.6.X.
Can you confirm me no plugin is activated on your WordPress website when you activate the theme, please?
Once these prerequisites are checked, please come back to me. 🙂