Unless someone has explicitly setup prioritization, your network does not know the difference between gaming data from your PC, a YouTube video on a tablet or Netflix on a TV. That TV might be a wired connection vs your WIFI or that TV might be a 5Ghz WIFI connection vs your 2.4Ghz.
The total amount of WAN bandwidth (down AND up) is used on a first come first served basis in-general. So you may just have insufficient bandwidth to your ISP.
It may be possible to prioritize your PC traffic, depending on what QOS capabilities your router has. BUT that only helps with your router, there could be obstacles outside your home network that are limiting your performance.