but sometimes there are some questions when we don't know the language very well哪里错了帮忙改下

when we don't know the language very well
when -that.

but sometimes there are some questions （when） we don't know the language very well
把when 改成that 因为questions=we don't know the language very well
所以其实是同位语从句 要用that 连接
你是这个意思么？
如果不改的话，句子的意思就成了 当我们不是很清楚那门语言时 我们会遇到问题。这样其实也可以的

when改成that,本句的中心语是“questions”，所以引导词用that,而不是用when.当定语从句修饰时间时才可以用when引导。

把when 改成that，这里是一个宾语从句由that引导。从句用来修饰questions

but sometimes there are some questions, for we don't know the language very well

中文想要说什么…知道你想表达才能改