Possible fix for bad internet connection only on PC?

situation is, i have very good internet, when i run Speedtest on my phone it gives me 300 MBPS but when i run it on my PC, it gets like 5. i suspect its because my PC is connected to the WiFi through a WiFi adapter. the adapter is called TL-WN321G, and i suspect that because its old and has 54MBPS the internet connection is so bad. can anyone tell me if im right in my assumption that this is why my internet on my PC is slow and if so, also recommend me some better wifi adapters? (connecting a cable to the router and then to my PC isnt possible)

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Thank You!