As you spent time on system your system gets down slow after a certain period of time.
This happens because of these three issues:

1. Temp files,
2. Infected files,
3. Fragmentation.

These three issues creates problem and your system gets down slow.
You just need to follow some specific steps for better speed and better Computer support.
Very first you need to delete temp files to delete temp files you can use CCLEANER.
To remove infected files you just need to run Updated anti virus.
You should run De-fragmentation to occupy unused space of the drive.