了 le (= suffix)
了 le (= suffix) can have different meanings depending on which kind of verb it is used with.
Action verb + 了 le (= suffix): The action is considered completed.
Stative verb, adjective verb or modal verb + 了 le (= suffix): Something has changed and a new state has begun.
It is like in English where the aspect of completion doesn't necessarily have to be linked to the past.
了 le (= particle)
If 了 le (= particle) stands at the end of a sentence, it is called particle. In this case, 了 le (= particle) always means that the entire situation which is described in the sentence ressembles a change compared to the previous situation.