Your maths is incorrect, I believe.
a=0.8g=8m/s²
s=1+3=4m
v²=2as=64 => v=8m/s, same as above, and necessarily so because the conversion from potential to kinetic energy occurs the same way.
½at²-s=0
4 t² - 4=0
So total t=1s
I'm not sure what "infinite storeys" has to do with that, you've...