The pendulum makes a free oscillation with a frequency of 0.5 Hz during which time

The pendulum makes a free oscillation with a frequency of 0.5 Hz during which time the pendulum moves from the extreme position to the equilibrium position.

The oscillation period is a period of time during which the body returns to the same point from which it began its movement.
The oscillation period depends on the frequency according to the law:
T = 1 / ν
Let’s define the oscillation period:
T = 1 / ν = 1 / 0.5 = 2 s.
This means that our pendulum takes 2 s. makes the following movements:
1.from the left extreme position to the balance position;
2. from the equilibrium position to the right extreme;
3. from the extreme right to the equilibrium position;
4. from the equilibrium position to the extreme left;
All these 4 distances are equal, our pendulum has passed only 1/4 of the period
t = T / 4 = 2/4 = 0.5 s.
Answer: in 0.5 s.