Need help with TP-link wireless router

Hello friends
i have bought TP-link wireless router TL-WR740N
some days ago

i am having problem with it some of the sites working well and opening but some dont open when i keep on refreshing the page it opens

i have this problem on both with wire or wireless using on 2 different computers but having same problem

i have reseted the router as well but nothing

please help meeeee

yes i am using PPPoE

thanks mate

try to change your dns, it seem dns problem.

i am using this switch by changing its default IP 192.168.1.1 to 192.168.2.1

and 192.168.1.1 is my modem ip

i have tried changing MTU Size to 1450 but still having this problem