Hello cesq, I am Telegram user and I noticed that Telegram seems to use own dns system to connect to the internet separated to the GNU/Linux system dns. This is why I also often experienced same experience as yours. The good thing there is that you are certainly connected to the internet (thanks to telegram's proof) (so I think your router is okay) but somehow other applications cannot. I have weak networking knowledge so this is only my guess.
My suggestion: 1) make sure your /etc/resolv.conf points to correct dns address 2) make sure your system dns resolver is working and not disabled 3) make sure no two network connections connected at a same time Cheers!