Hi rauf_anwar,
the logic of your code is good, but the double condition "touchdetected4 && touchdetected5 " is only true if the keys are pressed at exactly the same time. Otherwise the flag of the first pressed key will be set to zero in the function that concerns this key, and the double condition in "void loop" can never be met.
(pressing 2 touch at the same time with a processor that runs at many many Mhz is difficult !)