In short your browser can't find the websites. Slightly longer, DNS lookup has failed. Try a different DNS service for a while (this is normally an address set on your router).
I unplugged the router for a minute, then hooked it back up. After around five minutes or so, everything started working again.
It's possible your router is crap/failing/overheating and that's causing errors.
I replaced my basic modem/router with a low end business-grade router to get rid of this sort of problem
@ketsbaia started
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In short your browser can't find the websites. Slightly longer, DNS lookup has failed. Try a different DNS service for a while (this is normally an address set on your router).