Question My Internet Quickly Slows Down

[Blobwingz]

Hello soo back then I've used to have like 100MBPS+ staright on Speedtest also like 10MB/S on Steam when downloading game . But i start to notice that it slows down because someday I've downloaded a game from steam and i see that the speed is like 3MB/S=30MBPS
and out of curiosity i used Speedtest and now my internet speed would like quickly spikes to 100MBPS+ and it would quickly go down to like 20-30MBPS same for Upload.

Any Ideas what seems to be the problem????'

Edit: I use WIFI on the 5GHZ range
Also use a wifi dongle and it is the
TP-LINK T3U AC1300 MINI

 

[Fix_that_Glitch]

Have you tried resetting your modem?

 

[Blobwingz]

Have you tried resetting your modem?

I did not ima try it at midnight when people stop using the wifi

 

[Blobwingz]

I did not ima try it at midnight when people stop using the wifi

Ok uhh it did not worked ive reseted my modem/router and still spikes to 100MPBS and quickly goes down back again to 20-30MPBS