英语一般过去式 was were 后面加动词时用什么时态？还有被动语态什么形式，急

was /were 后面加动词时 只能加doing 或done
加doing 表示过去进行时；加done 表示被动语态。如：
I was playing tennis at this time yesterday. 昨天这个时候我正在打网球。
I was laughed at by my classmates. 我被同学嘲笑了。
所以表达“我以前打网球”应该是：
I played tennis.或：I used to play tennis.
第二句话是被动语态，也是过去时的被动语态。
被动语态主结构是“be +done” 其中的be 随着时态的要求而改变。
after doing sth. 中的after 在这里是介词，介词后的动词都需要加ing ，因为“介宾”的需要。介词后边要接名词或相当于名词的词作这个介词的宾语，动词加ing 就是把动词给名词化了。如：
I am good at drawing pictures.
Thanks for helping me.

你写的是错的 系动词后面加实义动词是被动语态 你想表达过去时的话要么把系动词变成过去时要么把实义动词变成过去时。
I played tennis才对
The program was started by Chinese young pioneers，是被动语态，是过去式被动语态

fish加ing是因为前面是介词after，在介词后加动词要变成动名词

I was play tennis.与 I was played tennis都是错误的。应为
I played tennis.
英语中，如句子中没实意动词，用be。即：实意动词与be动词不能同时出现。
The program was started by Chinese young pioneers，是过去式被动语态

after可作为介词，英语中：介词+动词ing， 为语法规则。

I played tennis。
The program was started by Chinese young pioneers，是过去式被动语态

after是介词，在介词后加动词要变成动名词，after+doing是一种固定各式，记住就行。