Hi Nawaf,
There is no input lag in KeyMander. What you are experiencing is usually caused by exceeding the game's maximum turn speed as explained here, due to your sensitivity settings being too high. I strongly recommend you first use our Overwatch profile and make sure to set the in-game settings as shown on our Overwatch profile page. Next, make sure to read that link above thoroughly as it explains all the different mouse settings and how they affect your in-game performance.

Ok, I understand that the problem is from the dpi,
how to actually change the dpi tough? Because I tried to change the keymander dpi from the software and yet there is no difference in game. Tested it on 1000 dpi, and 10000 dpi and no difference. And thanks, I appreciate your help.

You must make the changes in the software and then hit upload to send them to the KeyMander or the changes are not put into effect.