Internet is ruining the performance of the computer

[Romulator]

From what evidence you have provided, you seem to have a Worm. Worms self replicate, eating CPU, attaching themselves to files and when possible, become transmitted over the network. While not requiring a network to function properly, they work much better with one running.

You mentioned that you have already scanned your computer; if you have not done so, scan it with Malwarebytes. This thing will get rid of practically anything which could potentially cause problems. It is best to install MalwareBytes in Safe Mode.

Some viruses are also smart enough to know if MalwareBytes is running and kill the scan or startup process as soon as it begins. You can get around this easily by renaming MB's exe to something like "not_a_virus_scanner.exe" or something.

You could also check Google Chrome's add ons, if you have any. Enabling/Disabling some may also provide a performance boost.