Question

改错 My friend allowed me borrowing her umbrella If it isn't rain,we will go to the concert

I saw the accident happened
It's my turn cleaning the room

Answer 1

我直接把改完的题目写给你吧，纯粹手打，有错误或者疑问欢迎指出：
My friend allowed me to borrow her umbrella. If it doesn't rain, we will go to the concert.
我朋友允许我借她的雨伞。如果没下雨，我们会去听音乐会。
I saw the accident happening.我见证事故的发生（词组：see sb/sth doing看见某人/某事在进行……）
It's my turn to clean the room.轮到我清理教室了
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Answer 2

把happen的ed去掉 还有 把cleaning 改成to clean 上面那个 borrowing 改成to borrow。 另外在umbrella前面加名词an 没有了