Damped Harmonic Oscillation Question

If a marble is placed on the end of a horizontal oscillating spring and the harmonic horizontal position of the marble as a function of time is given as :

If x = A ( 2 pi f t)

where A is amplitude

f is frequency

and t is time in seconds

If the spring oscillates every 0.5 seconds and has a maximum displacement of 0.2 m

what is the frequency?

what is the velocity as a function of time ?

how do you write the equation in the form given above for the position of the marble as a function of time ?