How to shorten the width of a single pulse
What you want is called a monostable multivibrator, or one-shot for short.  You set it up to trigger on the leading edge of your signal.  It will the produce a pulse of fixed duration.

You set the duration with timing components, like a resistor and capacitor.  There are 74xxx series chips that are intended for exactly this purpose.  Look thru a selector guide.