SOS Bandwidth is fine, but i cant load specific websites

Hello,

I have my normal Internet speed 17mb download and 1mb upload, as usual.

I'm connected JUST by ethernet to my router, I downloaded a program to see how many devices are connected to my MAC and it says 4. My antivirus (avast) says they are 5, but 4 of them are... my pc?

I used avast and malwarebytes to find virus, but there were no viruses.

And, here is the problem.
I can enter on (examples):
-Twitch (it has to buffer very often, wich is not usual)
-Twitter
-Facebook
-This website
-Reddit
-Some others

I cant enter (No way to charge this webpages, neither pc or phone if i enable wi-fi):
-Yahoo
-Youtube
-Vimeo
-rated sites
-Hotmail
-Gmail

-A lot of other non important webs

I dont know if I'm getting ddosed, if i have a proxy and i dont know how to find it, or idk what the hek is happening, please help :(