I BOUGHT A CAR.
HE SAID THAT…
HE WENT TO CHINA.
Finished action is remotely equivalent to past tense and sometimes present perfect in English.
To indicate that the ACTION is finished, we put 了 /le/ right behind the verb.
ACTIONS are verbs like: TO BUY, TO GO, TO DRINK
ACTIONS aren’t verbs like: TO KNOW, TO WANT, TO FEEL
These are STATES and can’t be “finished”. They remain in the present form.
MORE DIFFICULT SENTENCES