Confused about breast feeding and pumping

I’m a FTM and I’ve read a bunch on how to breast feed and how often/how much/ etc so I kind of understand that. I’m not really sure about pumping though? When I’m on maternity leave do I need to pump and how much? How much extra should I have at all times? When I go back to work, how much should I pump while I’m at work? Do I pump after I’m doing breast feeding too?