@maznica
I can suggest you only general techniques which are used by our users.
For Site Speed Boosting Technique
Okay please make sure that Envato market plugin is deactivated in your setup.
if not then please deactivate it.It is having some issues with the current version of WordPress.
refer this tip to deactivate it:
https://www.ostraining.com/blog/wordpress/disable-a-wordpress-plugin/
The second step is to install this plugin "
query monitor"
refer this tip to know which plugin is actually putting a load on your server:
https://kinsta.com/blog/query-monitor/
Using caching techniques like memcached, opcache on server side might improve some speed .
Also try switching to PHP version 7.0 (not 7.1, it's unstable and is not compatible with the theme).
Also follow this caching tip:
https://vibethemes.com/documentation/wplms/knowledge-base/wplms-with-w3-total-cache/
Deactivate plugins that you don't feel necessary
Please also try disabling touch points if you have enabled them from wp-admin -> LMS -> settings -> touch points.
Use jetpack CDN for images.
or you can use WP Engine For Hosting.
You can ask your webhost as they can suggest you better