how to reset the TCCRnB values of the timers on Arduino Mega 2560?

I made a mistake changing the value of TCCRnB for all timers. So maybe it affects the delay() or the frequency of PWM… Is there any way to reset them? What can I do to recover the values? Thanks.

Is there any way to reset them?

Sure. Load a different sketch.

What can I do to recover the values?

Press the reset switch.