Question Laptop running really slow after 15 mins

[JohnSt55]

so i have an asus k550ik laptop the specs are:
cpu:AMD FX 9830p
gpu: amd RX 560
16gb ram

based on the specs and what ive seen on youtube and other websites i should be able to get 60fps on all esport titles and modern games on medium settings.but i cant
after 15 mins of use, the laptop really slows down to the point where even if i put everything on low settings, i cant get 60fps with 1280x720 resolution
(the monitor supports 1920x1080)
ive tried all that i could, went to power options,battery options,updated my drivers(i got a 15fps boost but not what i need) and a lot of other stuff but none of them helped.
my friends say that its because the laptop has only 2mb cache but i dont think that is that important
ive scanned the laptop and there are no viruses. the drivers are up to date
this is not a heat issue because after 5 hours of use the cpu is at 58 c and the usage is 85% while gaming and 15% while watching movies or listening to music.
please help me out ive been stuck with this bad performance for 6 months now (the laptop has always been like this even tho it was brand new)

 

[Shay Green]

Your cpu might be running at a low clock speed, try with the charger plugged in to see if there is a difference

 

[JohnSt55]

Your cpu might be running at a low clock speed, try with the charger plugged in to see if there is a difference

charger is always plugged in
i took the battery out when i bought it and have been using it while plugged in