what do i do!?

my boyfriend and i started having sex about a month ago. it was both of our first times. most positions are hard for us to figure out so we usually stick to just basic missionary. i wish we could do something else but i just don’t really know what i’m doing😂 also, every time we do it i can never actually get off. it feels good but it just doesn’t seem to be enough. and one of the biggest problems is i can’t get off and he finishes REALLY quick. any advice?