This app is pretty straight forward: enter your function as f(x), and it will show it’s first derivative, f’(x), also any number of magnitude of derivative you want it, fn(x).
With it’s simple UI, it couldn’t be easier to get what you actually want.
Try the app, and provide your feedback below.

It also supports many varieties of functions including (but not limited to):
sqrt(x)
xroot(x,n)
abs(x)
log(x)
log(x,n)
ln(x)
sin(x)
cos(x)
tan(x)
asin(x)
acos(x)
atan(x)
sinh(x)
cosh(x)
tanh(x)
asinh(x)
acosh(x)
atanh(x)
sec(x)
csc(x)
cot(x)

This app is a tool in the software Simple Grapher: https://www.microsoft.com/store/apps/9N0HT4ML82DS