Hello, @rima974,
Sorry for the inconvenience, But the thing is that the error you encountered in 504 is a server gateway error. It doesn’t relate to the theme. Please refer to these articles in order to understand the error and learn how to fix it: https://themeoo.com/how-to-fix-504-gateway-error-when-saving-pages-in-elementor/#:~:text=The%20main%20reason%20for%20this,this%20504%20gateway%20timeout%20error and https://elementor.com/blog/troubleshooting-wordpress-errors/
I hope you understand and your issue will be resolved.
Best Regards