Hi Ant222,
My English skill is not in the “grammarian” class but I will give it my best attempt to explain it. It may not may not be agreeable with the experts.
In many instances during casual conversations, we can bet by with simple past tense and no one will flag you for errors. However, to be grammatically correct, the right tense should be followed and observed consistently. Besides using present perfect to connect events from the past to present, sometimes, we will see past reference combined into a present perfect structure. i.e.
John seems to have forgotten who helped him 2 years ago when his lost his job. This is perfectly legal.
General simple present statement with timeless reference.
I have never seen movies as bad as this one!
I have tried many times to quit smoking but failed.
With time reference, past to present:
Jane has changed 3 jobs since the beginning of this year.
She hasn’t made any car payment for the past 6 months.
If you already understood the above, just disregard my post.