Computer has become slow - antivirus applications may be the cause
If your computer has become slow or sluggish the cause may be multiple antivirus applications. If you have installed free applications from internet you may have simultaneously installed a trial version of a virus protection application. You may have bought a antivirus application. In either case you have multiple antivirus applications running an scanning in you computer. This slows down your computer.
Remove unwanted antivirus applications from your computer.
Windows 10 has it's own antivirus application (Windows Security - Virus & threat protection). If you have bought another antivirus application then disable Windows 10 antivirus. Microsoft's instructions are here and at the end of page you can see how to disable virus protection.
NOTE: Please do not disable Windows 10 antivirus and threat protection if you do not have another antivirus application.