Because other machines do not have the issue it indicates it is likely the wifi or your machine. A test with ethernet would confirm the internet is fine and that it is not your machine itself. The key reason to test with a ethernet cable is to avoid spending money you don't have to. I would also try the machine right next to the router with the wifi, it could be a distance thing.
With wifi you have very few options. You need to make sure you have the latest driver. After that you need to decide if you want to just replace the adapter. Those tiny USB adapters are garbage so avoid them. The best ones tend to be the ones that come with a stand and USB cable so it can be set away from the computer. These also tend to have much larger antenna and full power radios unlike those micro USB devices.