There are many reasons why your computer runs slow. In most cases, your computer becomes slow after installing a new app or program. You may experience lagging after installing large software suites and high-end games.
The tips are listed in order, so start with the first one, see if that fixes the problem, and then continue to the next one if it doesn’t.
pls click on this and get all steps
https://support.microsoft.com/en-us/help/4002019/windows-10-improve-pc-performance
If the previous steps have not been understood and if the problem is not solved then click on this link below,
https://dailytechposts.com/computer-running-slow/
follow the steps in this simplest method in these posts and repair your own Pc DIY steps etc. It has helped me.