My net is good,but in game,i have like 4000ping.....

Although speedtest is a good way of checking your internet speed, it only shows your internet speed at 1 particular time.

Try running your cmd(command prompt) and try pinging to something for example google.

type ping google.com -t

see if your ping varies or is unstable. If it is, then there might be something wrong with your internet connection or isp.