oil pump

Red check oil icon flashes and sounds three times but only when I slow to 15MPH, never when I'm driving; oil level fine. That's happened the first time in the the last week but the slowing-blinking oil light and 3 beeps sequence now happening more regularly. Related? Yesterday only the turn...

I am needing to replace the Oil Pump in my beetle. I have checked two different repair manuals and both say to first remove the timing belt. Does anybody know why this is a necessary first step? Thanks!