Why are websites sometimes not loaded?

I do not understand why sometimes just websites are not loaded (see screenshot)

, Example: I'm going up my laptop, click on Microsoft Edge and want to open Google. But Google does not appear, but the error message "This page is not available". Immediately I try it with e.g. Youtube and it opens. Then I try again with Google, still the same error message. Then I choose another page from the bookmark and it works, another one does not. Strangely enough, all pages load when I wait 15-30 minutes. What is the problem? Internet connection (Wi-Fi) is available. Signal strength very good. Is it on the laptop?

Try it with another browser and then post the error message of the browser.