|"I personally have to deal with a slow computer and laggy gameplay when playing computer games"|
You didn't post your system specs but my guess is you're trying to play games on a computer that's not quite up to the task. The Radeon HD 6550D graphics integrated in the A8 is fairly weak. Lowering the gaming resolution & the game settings should improve your framerates.
"Slowness" could be caused by a lot of things - too little RAM, too many apps loading at startup & running in the background, virus/malware infection, etc. What are you using for AV protection & when's the last time you ran a deep scan (not quick scan)? Do you regularly use a cleaner such as CCleaner-Slim?
"I play a lot of games with viruses"
I suspect they are pirated games because retail game discs do not contain viruses.
"I've also discovered viruses that antiviruses (particularly Avast) does not detect"
Then maybe you should try an AV program that works?