The goalkeeper, while catching the ball, goes completely out of the penalty area into the penalty arc area with the ball still in his/her hands. how should the referee restart play?

Referee should start the play by "Direct free kick".

A direct free kick is a strategy for restarting of affiliation football following a foul. A goal might be scored specifically against the restricting side without the ball having first contacted another player. This is against an indirect free kick where the ball must contact another player before a goal is scored.

Around the world, there are many similarities between culture like norms, beliefs, values and physical object. Norms are the acceptable behavior of human, beliefs are acceptance of the statement that is true, values are the judgment of importance in life and physical objects are used to define what is the culture of people.