One of the most difficult tenses to understand in English grammar is Present Perfect Simple. It always indicates a very strong connection between the past time and the present time.
Here are some easy examples to help you understand better guys.
If you say:
‘I have always wanted to be a singer’ it means since I was born until now and I still want to be a singer.
‘I have never been to Australia’ it means since I was born until now. (We express experience)
Similarly with questions, we can ask about someone’s experience: ‘Have you ever been to Australia?’ It means since you were born until now.
There are also many past-present time result sentences:
‘I haven’t I cleaned up my room today’ it means since the morning started until now, it’s maybe evening and my room is still dirty, lol
‘Have you finished yet?’ It means since you started doing something until now and are you ready now?
My favourite Present Perfect + since+ Past Simple sentence which I recommend that you guys remember is:
‘I have met many nice people since I came to Canada’ 
(It means since I came to Canada until now, past and present time are connected and it also means experience)
Hope this helps.
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Greg