There are Many Reasons For Slow Computers & Many Programs are Running In The Background.
Remove Program From End Task Manager.
Delete Temp, Prefetch File
Method 1:
Press Windows Key + R or Click >Start Menu>Run Command
Temp
%Temp%
Prefetch
Write This, Delete Junk File
Method 2:
Right Click On Start Icon>Click On System>Storage>Select Temporary File
Remove It
Scan Malware
At The Present Time,There are many PC Affected By Malware.You Can Use Malwarebytes To Scan Your PC for Malware
Quick Tips:
Upgrade your Ram
Upgrade your Hard Disk (SSD)