如何理解这句话里面的how back then.

Question

Okay, we've been discussing films in the 1920s and 30s, and how back then film categories, as we know them today, had not yet been established.

Answer 1

您好
*******************
后半句的主句构架是how film categories had not yet been established.

back then 作时间状语成分 翻译成 “那时候的”
as we know them today, 做插入成分
*******************
欢迎追问

Answer 2

　　用how,是说那时如何如何的如何部份,形容那年代的
我们在讨论1920和1930年代的电影,和如何那时现在我们知道的电影分类并没有被定下来。
　　指的是以前那时候~

Answer 3

主句结构错误。主句若是how film categories had not yet been established，那这句子无主语了，因此错误。
正确主句应该是film categories had not yet been established.
how back then此处应作为插入语，意思: 那时候怎么样呢？语法上，此处的how是形容back then这一状语的状语，而不是平常我们惯用的引导从句的how

Answer 4

现在让我们追溯到这一时期电影目录