This is going to be a long answer, so please bear with me.
Wi-Fi is a radio frequency that is prone to interference and degradation the farther you are from the source. All of the walls and distance will dramatically lower your signal strength.
Extenders/repeaters can help, but I don't really recommend them. For one, they're slow. They will cut your speed in half since Wi-Fi is a half-duplex communication. That means it can only send or receive at once, but not both. Its like a walkie talkie where only one person can talk at a time. Additionally, you would need to place your extender about half-way between your router and your computer since if it can't receive your main Wi-Fi signal it won't work at all.
There something called a Wi-Fi mesh network which has a base station (plugs into your router) and the receiver unit goes near your room. These devices create their own internal wireless network that they use to communicate with each other. The receiver unit will create a Wi-Fi network that your devices can use, and in turn the units use their back-haul network to send/receive data. These generally work better than extenders/repeaters, but they are significantly more expensive. A good setup can easily cost over $250+ depending on brand and model.
An alternative that can help would be to install some Powerline Ethernet adapters. They work in a similar fashion to the Wi-Fi mesh network I described above, but instead of a wireless communication, they use the electrical wiring in the house to communicate with each other. Some of the adapter models have built-in Wi-Fi but most generally just have 1-2 Ethernet ports that you can use to plug a Wi-Fi AP, network switch, or PC into it. I used a setup like this and it worked ok. Often times, the adapters would disconnect from each other or "freeze" for a few seconds. It was annoying. Additionally, it took some time to figure out an ideal location to plug the adapters in. On some outlets, they just wouldn't connect at all. In some they would intermittently connect, and in a few, they worked, but were slow. Also, if there's a lot of electrical noise in the electrical system of your house, it can drastically affect your speeds. Things like AC systems, refrigerators, compressors, etc can cause issues when they kick on. Your mileage may vary with this setup.
IMO, the best way would be to run an Ethernet cable from your router to where you live and install an access point/network switch. This way, you don't have to worry about signal loss or degradation. Ethernet has a max length limit of 100M (~328 ft) before it begins to degrade.
Most routers have a QOS (Quality of Service) function which allows you to give certain devices or applications higher priority over others. You could essentially give your PC higher priority on the network for improved network performance in those games, but you have to have access to the router to set it up.