A slow PC is rarely one problem. It's usually a pile of small ones, and fixing them in the right order saves you from buying a new computer too early.
Start with what runs at startup
Open Task Manager with Ctrl, Shift and Esc, go to Startup apps, and disable anything you don't need the moment Windows starts. Chat apps, updaters and game launchers are the usual suspects.
Then check the disk
If your PC still has a spinning hard drive, replacing it with an SSD is the single biggest upgrade you can make. It costs less than a day out and makes a five-year-old laptop feel new.