The browser has to wait for the first response
Before the page can render, the hosting environment has to accept the request and begin returning data. Slow server response adds delay before the visible page-loading work even begins.
Performance is a system
Good results come from the combination of hosting, caching, application design, image handling, scripts and network delivery.
Measure the live environment
Performance should be checked on the real deployed website because third-party scripts, content and hosting conditions all influence the final result.