longboard to shortboard

[fisherguy]

ive been longboarding for about a 3 weeks now. probably around 5 times a week and 3-4 hours every time, and im able to stand up on waves up to 4 ft face and carve up and down the face. i have a 6'6 dennis pang t and c shortboard...looks like its from the 80s-90s but in good condition. im 5'11" 170 pounds. ive tried using it and i can catch the wave, but im having extreme difficulty standing and doing the bottom turn. im wondering if
1) shortboarding is a huge step from longboarding and it's normal to take a long time to adjust
2) i should stick with longboarding for a bit longer
3) the board is too small

[Driftingalong]

1) and 2)...