Sorry, this will be entirely in English. We use past tenses, with a past time, to describe the past... and ONLY the past. The past is history. Please remember this, because then you will understand present perfect more easily. Present perfect describes NOW. The present tense comes from "have/has". We use present perfect to connect the past to the present. Some situations are: - a situation began in the past and is still the same now. - the present situation is a result of a past event. - past events are important or relevant now (you'll see this in news reports: events that happened very recently).