I kind of have an idea of when 了 and 过 should be used but it's mostly on a case by case basis, and I don't know the exact rules. So if I want to express something that happened in the past, when ...
I came across the following sentence: 我病了。 I know 了 has many functions, and I believe one of them is a completive marker (past tense). But this sentence is apparently in the present, based on the ...
In this sentence: 他曾经在北京学过两年汉语。 what's the role of 曾经 ? I understand that 过 already implies that the action happened in the past.