Installing antivirus makes a machine (a little bit) slower, since it uses resources. Most people accept that, because it prevents more serious problems.
If the machine was very slow already without antivirus it's a potential warranty issue. Reset it back to factory conditions and if no luck, back to the shop to have it fixed.
My computer is very slow from the day I bought it, I have installed Anti-virus but no use.
Processor- Intel(R) Core(TM) i5-6200U CPU @ 2.30GHz
Installed RAM 4.00 GB (3.87 GB usable)
Any tip will be great.