In the section finished action we learned that 了 <le> right behind the verb serves as an indicator of a finished action.
了 <le> placed in the end of a sentense however works as a marker that a situation has changed.
<Wǒ bù chōuyān le.>
I not to smoke le.
I DON’T SMOKE ANYMORE.
<Tā lái le.>
He to come le.
<Wǒ jīnnián 29 suì le.>
I this year 29 years le.
I AM 29 YEARS OLD.
Previous sentence might seem a bit strange – why do we use change of events when talking about the age (which lasts for a year and hasn´t just changed)? It is because 了 <le> indicates that situation has changed (or will change) to the state that it afterwards is (or will be) in. That´s how it helps us to express that the state still persists (or will persist).
<Nǐ zài Ōuzhōu duōcháng shíjiān le?>
You in Europe how long time le.
HOW LONG HAVE YOU BEEN IN EUROPE (SO FAR)?
<Wǒ zài Ōuzhōu shí ge yuè le.>
I in Europe ten months le.
I HAVE STAYED IN EUROPE FOR TEN MOTHS SO FAR.
Anyway, situation can change in the future as well, in that case we also use 了 <le>.
<Kuài yào xiàyǔ le.>
Fast (soon) yao to rain le.
IT IS GOING TO RAIN SOON.
<Wǒ mǎshàng yào zǒu le.>
I immediately yao to leave le.
I’M LEAVING IN A MOMENT.