slow page - high Web browser is waiting for data from the server

[pkubik]

Hi,
Please help with the speed of loading pages. I installed the latest version of joomla and virtuemart, PHP 7.1, but the pages load slowly. Page runs on the server itself. I can set many things, but what are the right ones? or is joomla incorrectly set? link to rate page rate: https://tools.pingdom.com/#!/bSCqDc/obchod.i-nehty.cz Thank you for your help. Petr.

[Studio 42]

Do you have try without jchoptimize ?
I have sometime better result without it(not for pagespeed socre but page load) if you use http2
Another problem can be because your use a poor shared server? The main slowdown is the main HTML page.

[pkubik]

with jchoptimize the page is faster.

Interestingly, when I activated the plug-in cache what is in Joomla by default, the loading time has improved significantly. The problem is that the basket does not work properly. When I add the goods to the basket on the main page, so I do not see the basket, I have to go to the subcategory or the goods detail and then update it. Does anyone know in the System Plugin - Cache on the Advanced tab to exclude the cache for the shopping cart? I have the cache off in my cart module.

[Studio 42]

You should try Joomla debug, so you can see the problem(you have a report with the time needed per queries to detect slow queries) and Virtuemart debug(you can set only admin) display you some informations too.
Try to disable some modules or vmcustom plugins and system plugins, to check if this is not the problem, because this are called each time and can slow down your whole site.
About Jchoptimize, this can break your webshop, eg your basket problem can come from jchoptimize.