before means "antes" and always comes at the end of sentences and questions, She has been in Argentina before, Have you tried this food before?

Already means "ya", it goes between the auxiliary has/have and the past participle verb in affirmative sentences and between the subject and the past participle verb in yes/no questions, we have already watched this movie, have you already done your homework?

yet means "aún" or "todavía", is used in negative sentences and in yes/no questions, and always comes at the end, I haven't gone to paris yet, have you visited Mexico yet?

ever in questions means "alguna vez", in affirmative sentences means "siempre", and in negative sentences means "nunca", Have you ever tried Beijing duck?, I've ever wanted to have a car, she hasn't ever tried that food