After installing/upgrading an app or theme, you might notice an issue that site layouts on several pages will be broken or display incorrectly.
This happens because you need to Rebuild Core Theme to apply styles of newly installed app/theme to your site.
To perform Rebuild Core Theme, from Admin CP >> Maintenance >> Rebuild Core Theme.
Wait a little bit until the process finished and it will redirect you to Admin CP Dashboard.
You also have to clear cache of your site to get rid of old styles and force the site to use the newly built style.
From Admin CP >> Maintenance >> Cache Manager >> Clear Cache.
Reload the page, all the layout issues should be resolved by now.