Why am I lagging

When I go on speedtest by ookla to check out my speed, I have around 20 mbps while ping shows maybe around 14. So why is it when I enter a league game I have 300-500 ping. That's what happens half of the time, the other half, my ping is around 30-40 with lag spikes. I tried lowering the graphics, closing all of my tabs, reconnecting but it won't help.

Much appreciated