Hello Dmitry! How have you been? Well, if I understood your question, I guess this is almost always hard for us non-native speakers to figure out. As a rule of thumbs, we use the present perfect with a lot of different senses and meanings. For example: 1. I have just seen a ghost - (it happend a few minutes ago) 2. Have you ever seen a ghost? ( I don't know whether or not you did) 3. I have already done my homework ( I was expected to have it done) 4. I have never eaten snails ( It never happened before) 5. I haven't eaten my food yet ( I was expected to have it) 6. I've been a teacher since 2001 ( For some time with a specific date) 7. She has been a manager for ten years (For some time with an aproximated time) As for the Present Perfect continous we will always think that the situation started and we still have either consequence or effect over the present. For instance: "I have been waiting for you since I got here, an hour ago!" she has been doing the same old thing each and every saturday. I hope I have helped you understand that somehow! Cheers and have a nice weekend.

I suggest that you look for keywords and key phrases that tell you when to use present perfect (if the concept "blows your mind", then I assume you are still trying to understand present perfect, and you'll discover past and future perfect later). Typical key words which you normally see with present perfect include: since, already, yet and just.