Hello,
Although common solutions to your problem has been written above, I'd like to give some advices too.
You can try to clear your DNS cache.
You can do this by running Windows Command Prompt (CMD) as administrator, and run the following command: ipconfig /flushdns
If you are using Wi-Fi as the connection method, switch to wired connection with an Ethernet cable if you can.
This will improve your overall connection quality, and therefore, download & upload speeds and lower your ping.
If you can't switch to wired connection; make sure no other devices are connected, and make sure your router isn't placed near anything that could interfere with signals (ie. cellphones, microwave, TV)
try to clear your ARP cache.
You can do this by running Windows Command Prompt (CMD) as administrator, and run the following command: netsh interface ip delete arpcache
You can try to clear your PC's temporary files by using software like CCleaner or Revo.
At last, if none of these steps seems to be working, plug out & restart your router after waiting for a couple of minutes.
Hope it helps!