Is gesturing or saying "Okay, no problem" – when pretending to understand what others are saying while that is not the case – considered a lie, and what is its ruling?

One should listen to the speaker and not be preoccupied with anything else. Asking for clarification when there is ambiguity is not a flaw; rather, it may be better than pretending to understand, because the Prophet, peace and blessings be upon him, said: "The one who pretends to be satisfied with what he has not been given is like one who wears two garments of falsehood." Constantly feigning understanding becomes a habit that prevents proper comprehension and is considered a deficiency. One should not be content with ignorance or arrogance that prevents asking questions. However, it is permissible to feign understanding and nod if the speech is unimportant and does not contain anything forbidden, or out of compassion for the speaker or to save time.