When you use "ever' it means you are asking if someone did something at least once in their past, when you use "yet" it means that you knew that this person had plans to do that something and you are asking to know if he had done it or not yet. Hope this helps

Three sentences: 1) Have you been to Germany? 2) Have you ever been to Germany? 3) Have you been to Germany yet? 1): this is asking about an undefined time period with no expectations. If I ask you with no context, "Have you been to Germany?" I probably mean "during the period of your whole life". But if you first say, "I've been to a lot of countries in the last five years," and I ask, "Have you been to Germany?" then I probably mean within the last five years, since you were talking about that time period. 2) Since I said "ever", this emphasizes that I'm asking about the time period in your entire life. I'm asking if you have been to Germany at least once since you were born. It is the opposite of "I have never been to Germany." (Except in the affirmative, we don't say, "I have ever been to Germany." Instead, we just say that we have been there.) 3) Since I said "yet", this implies that I expect you to go to Germany at some point. Maybe you told me your plan, or maybe I just think you should go there. So I ask if you've been there yet. If you say, "I haven't been there yet," it implies that you are planning to or hope to go there at some point in the future.

I would ask: "Have you ever made the journey to London?" if I want to know whether you have had the experience of making the journey to London even once in your life; but... "Have you made the journey to London yet?" if I am expecting you to have made the journey or to be making the journey shortly (so the question is about timing of an anticipated event) - and this question could be asked this way regardless of whether I thought, or didn't think, that you had already had the experience of making that journey on previous occasions.

The difference between the two adverbs "ever" and "yet" is that "ever" is = always, while "yet" is usually thus far; up to the present; up to some specified time. The adverbs "ever" and "never" express the idea of an unidentified time BEFORE NOW. It is always placed before the main verb (past participle), for example, 'Have you ever been to Germany?' "Yet" is used in negative statements and questions, to mean (not) in the period of time between before now and now, (not) up to and including the present. It is usually placed at the end of the sentence, for example, 'Has he arrived yet?'