Why my games are not running properly if they're not running in the POWER SAVING option?

Everytime I select de HIGH PERFORMANCE option in Switchable Graphics in any game, it doesn'r run well, its slow or blurry, is there any way to desactivate the integrate video card and make the other one primary? I have this laptop:

 

DELL Inspiron 5765

Processor: AMD FX-9800P RADEON R7

Memory RAM: 16 GB

Primary Video Card: AMD Radeon R7 Graphics (Integrated): 512 MB

Discrete Video Card: AMD Radeon R7 M440: 4096 MB

 

Thank you for your help