Hello, @Kazi Sabit,
Your site speed score is very low check these images: https://postimg.cc/hJSvtJFC and https://postimg.cc/rdFyLvW3 the issue you mentioned is quite possible because of this speed score. You have to optimize the site speed in order to solve your issue.
To optimize your site speed score you can use the WP Rocket plugin here is an article to understand it better:
https://xstore.helpscoutdocs.com/article/100-how-to-speed-up-my-website
https://xstore.helpscoutdocs.com/article/128-how-to-improve-wp-rocket-settings-with-xstore
Regards 8Themes Team.