What is the difference between the simple past and the present perfect indeed?
1- definite time and indefinite time? can simple past be used with indefinite time adverbs?
2- can "just", "already" and "yet" be used with the simple past?
3- if yes, why do you think they are mostly associated with the present perfect in most grammars?
4- I think there is a difference between AmE and BrE about this. what is that?
5- Are "I washed my car" and "I have washed my car" grammatically correct? Is there a difference? if there is, can you talk about the situations explaining that?
6- What are the situations in which we choose one rather than the other?