1. Chinese verbs do not have inflection in form,the particle “着(zhe) ，了（le ），过(guo)” is often followed by a verb to indicate various additional meanings.However,not every verb can take “着(zhe) and 了(le ) .
2.the aspectual particle 了（le ）is suffixed to the predicate verb ,indicating the completion of an action.The basic patten is as follows:
subject+ predicate(verb)+（le ）+ (object)
ex.他成功了。(ta cheng gong le ) he succeeded.
2.The negative form of the perfect aspect of an action is：没(mei)+predicate(verb)
Note that the aspectual particle 了（le ）after the predicate verb should be dropped in the negative sentence.
ex. 我没结婚。（wo mei jie hun）I'm not married.
ex.他没成功。（ta mei cheng gong ）He didn't succeed.
3.The completion of an action may either take place in the past ,present .The aspectual particle 了（le ）only shows that an action is in the state of completion.If the time is not specifically pointed out , it normally refers to "the present","the time of speaking".
It should be specially noted that a time noun or phrase must be used to give a clear time reference.