A slow computer is usually caused by one of a handful of things. Most are easy to fix yourself.
Most common causes
Too many programs starting up automatically when you turn on the PC
Not enough free storage — less than 15% free space hurts speed
Old hard drive (HDD) instead of a modern SSD
Too many browser tabs or background apps open
Windows hasn’t been restarted in weeks
Free fixes to try today
Restart your computer (a full restart, not just sleep)
Open Task Manager → Startup → disable programs you don’t need
Delete files from your Downloads folder
Run Windows Update — updates often include performance fixes