From soft top to shortboard

So i'm 5'10" 140 pounds, and very fit. I've been surfing a 7 foot soft top for about a month and i can catch waves head on no problem and standing up isnt an issue anymore. I got a 5'9" rusty dwart from a friend for dirt cheap but i'm having trouble gettin into the waves, and standing up is a whole new game. Am i making the transition to quick?
(I surf in northern Florida, the waves are pretty shitty rightnow but i'm having trouble even catching those)
(I surf in northern Florida, the waves are pretty shitty rightnow but i'm having trouble even catching those)