Prosucts Do not Open fast

I have checked your sites and there are a couple of things I notice;

1. Avoid lazy-load for above the fold images. Above-the-fold images that are lazily loaded render later in the page lifecycle, which can delay the largest contentful paint.
2. in the JS console I see this “The resource https://widget-v4.tidiochat.com/1_123_0/static/js/chunk-WidgetIframe-2b15c4d844c6b675e362.js was preloaded using link preload but not used within a few seconds from the window’s load event. Please make sure it wasn’t preloaded for nothing” For this I would recommend you defer loading of the js file by going to Minify>> Defer Javascript.

Here is our guide on how to increase your page speed with WordPress Optimize: https://updraftplus.com/how-to-increase-website-speed-with-wp-optimize-plugin/

Hello, I asked about the point 2 you mention. It is not them that delaying the product page they said.

As for the first one. What can I do exactly to resolve it?

Do you use a plugin for lazy load? WPO does not have it on the free plan.
The following are features on the free plugin that should help: minify CSS/JavaScript, defer non-critical CSS/JavaScrip