We can help related to Toolset and it's performance, not related to a website's performance in general.
For Toolset, if you notice that your site is slow, and suspect, or want to exclude, Toolset from the possible source of issue, please proceed as outlined:
1. In a Perfect case, duplicate the site to a staging server
2. If that cannot be done, backup the site
3. Disable all Plugins and enable Twenty Seventeen Theme
4. Make sure, and this is important:
- that MU (Must Use) and other "non default" plugins are disabled as well
- those plugin, specially Cache Plugins, often cannot just be disabled (they require more action to really be deactivated)
==> For example tis is how you remove TotalCache:
hidden link
5. Make sure as well Server side, there is no caching active, and you run a compatible server:
https://toolset.com/toolset-requirements/
6. Test again.
If now a performance issue persist, it may very well be due to Toolset.
Otherwise, the issue is due to something else and cannot be handled here.
If the issue is due to Toolset, or may be, you could follow these steps:
1. Disable Toolset Plugin one by one
2. Check by which the issue is gone and check what that Plugin you just disabled does.
For example, if when you disable Views, the issue is gone, then most likely, you display a View or Content template on the pages that are slow loading.
Those Views would then be the source of the issue.
==> I always warn from customized image sizes, for the reason that they add a second each image, in load time
This happens in Views when you have lots of images listed, and for each image, you did pass a Custom Size in the ShortCode with which you display that image.
In that case, the code generates the new custom size each time the image loads.
I suggest, if you use that, to change those sizes in the ShortCodes to a predefined, set by the Theme Thumbnail or Image size.
That often solved performance issues in the past.
For more generic details you can also refer here to the docs, or ask me any detail if you are not clear about something:
https://toolset.com/documentation/user-guides/front-page-filters/how-to-use-views-parametric-search-on-large-sites/
https://toolset.com/forums/topic/can-toolset-can-handle-a-big-db/#post-379949
