here is no clear sign such as v.-ed or v.-ing to tell the difference between the past, present and future in Chinese. But please don't worry about that, there is still some point you could get the meaning. e.x. 我上过课了。（过-Past） 我上着课呢。（着-Present） 我要去上课了。（要-future）

I did something 我做了...事情 I am doing something 我正在做...事情 I will do something 我打算（将要）做...事情

我吃一些面包。 i eat some bread. ----- present 我吃了一些面包。 i ate some bread. ----- verb + 了 = did 我正在吃一些面包。i am eating some bread. ------ 正在 + verb = be doing 我 将要/打算 吃一些面包。i will eat some bread. ------- 将要/打算 + verb = will do

be using resultative ending or indicators of time

There is no strict clarification among these three. Usually we will use "了” to show something happened,for example,我吃了；or if there is a wold showing the time,"了“is not a must,for example,我昨天在家里吃饭。but please pay attention to the following,if something you didn't do,you don't use "了”，for example,我没吃早饭。We use“在+Verb"or"正在+Verb" to show present,for example,我在吃饭，有事等一下再说。And we usually use "打算、即将····” to show future,but not a must as well,for example,我明天去香港！