Past Simple or Present Perfect?

Do you know the difference between Past Simple and Present Perfect?
The past simple is used when we describe an action that started and finished at a specific time in the past, whereas the past perfect is used to describe an action that started in the past and continues to the present time.

The past simple can be used with phrases relating to finished time, such as:
yesterday, last week, last month, in 1999, three days ago

The present perfect can be used with phrases relating to unfinished time, such as:
this week, today, this year

Already, yet and just are usually used with the present perfect tense, but in North American English they can also be used with the simple past tense.

TIMESTAMPS
00:00 - Introduction
00:11 - Diagnostic test
03:32 - Explanation
04:28 - Present Perfect
06:26 - Past Simple