i tried many methods but i'm not able to regenerate frequency ore than 50Hz. thats why i'm asking in this portal.
As I've reached several MHz myself on a 16 MHz processor, all I can say is "you must be doing something wrong".
Now if you go and read the sticky as pointed out above, and post the info requested, we may actually ha ve some pointers on what you're doing wrong, and how to do it better.
So that'd be the code you're using, and a schematic of how you've wired those BTN8982 half bridge ICs to your motor and your arduino, and of course which incarnation of arduino you're using.