My computer doesnt connect to the internet??!?

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I am getting really frustrated now... A few days ago my computer was working fine, and then i started to notice that it got slow, and i have xfinity so my wifi is really fast. I reset my router and its still slow. Later my family said that their cell phone and computers were working fine.

I then got this error message on troubleshoot:
"Your computer appears to be correctly configured, but the device or resource (DNS server) is not responding"

I tried everything! and its only MY computer in my house so its not the wifi or router, just my internet. Please someone help i barley have any connection to send this Question. Thank you

PS ( my wifi bars say their full connection but i dont have any wifi)