I currently use a crew bike co track fixed bike but i want to upgrade to an e-bike i want one that can go long distance but not too heavy because i am a bike messenger in nyc so there are frequent hills and bridges
Sidewinder Jerry
Just like we here tell people to go to a reputable bicycle shop for a pedal only bicycle; I'll advise you to go to a reputable ebike dealership in NYC.
New York requires ebikes to be made by a legitimate manufacturer. Meaning no self built ones. If the ebike is over 750 watts and/or you exceed a speed of 20 mph NY state considers it to be a limited speed motorcycle. Which will require a motorcycle license, insurance and registration.
An ebike isn't an upgrade for a bicycle messenger. The better ones only have a 30 mile range at best and maybe 2 hours of actual use. You want light weight? That isn't going to happen. Motors and batteries add weight which you'll hauling around when your battery goes dead. If you work 6 hours 5 of them will be spent carrying the extra dead weight.