@Happi do you have problems when the only traffic to/from the Internet is your gaming traffic (e.g. all other devices are disconnected, and on your gaming device no programs apart from your game are running in foreground or background that could be accessing the Internet)?
If you have problems even when all the bandwidth is dedicated to your game, SQM wouldn't help, maybe your ISP network is congested which would be outside of your control, but you could try switching to a different ISP.
If the problems go away in that set up, you should be able to shape the traffic to fix the problems, so that it'd work as if your game had the whole bandwidth to itself. You could mark your gaming traffic with DSCP on your gaming device and apply strict prioritization on the router, so that other traffic would be prevented from competing with your gaming traffic (other traffic would only use the bandwidth not needed by your game), if you do it properly, you'd be able to play games with minimum latency while uploading/downloading heavily (e.g. running p2p file sharing programs like bittorrent). More information can be found in the post below