Internet pages won't load and server errors

Hello everyone, I've got a problem that's been persisting on my macbook since I changed of internet provider, here's the sketch:

My browser doesn't load internet pages regularly and I constantly get server errors. I have already changed the DNS adress to OpenDNS and the google one, two or three times; I've created another account and the problem persist. When I deactivate the Wi-Fi and turn it on, I get fully freshed internet loads, but for a minimum time.

My iPhone too gets slow internet functionality (and usually doesn't load any Safari page) when my macbook is using the Wi-Fi, so, i close my mac, and the iPhone works right.

My brother have a Dell laptop and it works right and sleek, or so he tells me. But yeah, do you have any idea what's happening, please?

EDIT: It usually starts to fail when I enter Youtube, or The Verge, or even the New York Times. If I only use it to enter Facebook it works pretty great. Also, the speed (10Mbps) works fine, although one day I got 0.00 at upload speed, every other day i get around 0.97mbps.

 

Fixed!

I finally fixed it! I entered my modem preferences and deactivate the IP overflood option. My machine is smooth again.