Liberia has changed a lot, but people still want to be treated with respect. Nobody eats alone so when you have someone with you, it is best to tell them "come, lets eat." Never return a bowl or plate empty to someone who have given you food in it. That is not done.
The biggest thing is that Westerners think that because Liberians avert their eyes and do not look people in their eyes, that Liberians are lying. Custom and upbringing dictates that Liberians do not look people directly in their eyes. That is disrespectful. So no, they are not lying, just being courteous.
Never call a person older than you by their first name. It is always Aunty, Uncle, Mr or Mrs. or Ms.