You either got the wrong keyboard model, plugged it in incorrectly or the issue was not with the keyboard in the first place. What do you mean about lag in writing? They keyboard works but typing is slow, or are really only two buttons are working? If only two buttons work, re-seat the keyboard, test with an external keyboard to see if that works fine, contact the seller of the keyboard and make sure you have the right model for your laptop, maybe exchange it.