Hello, @Muhammad Ali,
Alright, let me explain to you why your site speed is low.
First of all, check our demo speed: https://postimg.cc/5HCBf3Sy it is well optimized. Now check your site speed score: https://postimg.cc/dL3Tq6qF as you can compare both images your site speed score is very low. I have also underlined the cause of your site speed score. You have to optimize these things in order to speed up your site.
Now, The site speed is based on the site content and the server. It is necessary to use a light-speed server with a good configuration to make the server response time less. When we use third-party plugins it also affects the server response time. We make our theme with huge functionalities so that our customers try to avoid third-party plugins. In your case, I can see that the server response time needs to optimize also, the JS, CSS, and images too. If you check this image: https://postimg.cc/fktNDS6F it tells you the cause and how can you fix it.
You can use the WP Rocket plugin for this it will help you to optimize the images, CSS, and JS code of the site also it will help you with the cache too so that all the issues will be resolved and server response time will automatically low and you will get a desire results of your site speed.
To know how the WP Rocket plugin works with our theme please follow this article: https://xstore.helpscoutdocs.com/article/128-how-to-improve-wp-rocket-settings-with-xstore
I hope you understand.
Regards 8Themes Team.