What happens to the capacitor’s output if the input signal’s frequency is higher?

Capacitor's impedance depends on its frequency.

Impedance of capacitor=1/(2×pi×frequency×capacitance)

Pi=3.14

If frequency is increased ,impedance of a capacitor reduced.
(See the above formula, impedence and frequency are inversely proportional)so,current flowing through the capacitor increases.

Theoretically for a very high frequency signals,impedence offered by the capacitor is zero.