Could anyone explain have + pp in all its..depth?

This particular feature of English distresses me.
This is nonexistent in Korean..
For example, If I say
you have forgotten your respect for me.
This surely refers to the past,
but why not
you forgot your respect for me.
Because it may indicate that he/she regained that respect?
which is not what you mean,
Because Have+pp only refers to the present in relation to the past?
which means that lack of respect is still going on?

If there are other aspects of Have+ pp that you want to point out
,which you are not conscious of on a daily basis
please don’t hesitate to teach me. Thanks!