Help with new router

[Issy]

I really hope someone can help me with this. I upgraded to new Internet speed and yesterday I had it installed. Of course a new router was places insread of the old one. But since then I am having trouble accessing my usual sites (as book marked) like here D-A and Facebook and others that I go usually everyday. It tells that not being able to open and asks me to reload the page which sometimes work and sometimes not. Is it problem with DNS again? Appreciate any help I get.