last two day i experience wired behavior from network.

1- can not refresh repositories, list update or update the system. it return some message(simply can not Reach the links).
2- when try use browser some websites can not reach it (did not load). but when i use proxy it open normally.
3- when try open same sites on mobile android system over wifi get same results. but when i turn off the wifi and open the mobile data network the website load(i did not test all website).
4- after loading the website using mobile data network on android i turn off the data and back to use the wifi for android system again and this time when try open same website it open.
5- so i clear the browser history (cookie and all thing) and try open same website using wifi on android system (mobile) but it did not open (load).
6- the blocked websites continue trusted websites (like this site, and some government site).
7- i use google dns, try use different dns provider but same results.

now every thing back to work normal but i try understand what happens
also if there's something i can do
thanks in advance