Start by ensuring your cream cheese is at room temperature. This step is crucial for achieving a smooth, lump-free filling. If the cream cheese is too cold, it will not blend well with the other ingredients, resulting in a lumpy texture.

Place the softened cream cheese in a mixing bowl. Use an electric mixer or a hand mixer to beat the cream cheese until it is smooth and creamy. This should take about 2-3 minutes. Be sure to scrape down the sides of the bowl to ensure all the cream cheese is evenly beaten.

Gradually add the sweetened condensed milk to the cream cheese, continuing to beat the mixture until it is fully incorporated. The filling should be smooth and creamy with no lumps. This step is essential for the cheesecake's texture and sweetness.

Once the filling is ready, pour it into the pre-made graham cracker crust. Use a spatula to spread the filling evenly, smoothing the top. Be careful not to overfill the crust, as the filling needs to stay within the edges.

Wash and dry the fresh berries thoroughly. Arrange them on top of the cheesecake filling in an even layer. You can mix the berries for a colorful presentation or create patterns with different types of berries. The fresh berries add a burst of flavor and a vibrant look to the cheesecake.

Cover the cheesecake with plastic wrap or aluminum foil and place it in the refrigerator. Allow it to chill for at least 4 hours, or preferably overnight. Chilling is crucial as it helps the cheesecake set properly, making it easier to slice and serve.