For those who got the Gateway Timeout 504 error try Ctrl + R (Windows) Cmd + R (Mac) or try right clicking the page and [Refresh] or try using the 'Reload' button if you have one on your browser (right of address bar).
You can try these even if you did not get the 'gateway timeout'. I have used them on Bing, Google and DuckDuckGo (not saying it will improve the fast/slow problem but it may be an improvement).