Detailed; lag behind

Hi,

1) There's a word in German that can be used to describe a detailed exam or study materials -->umfangreich.

I was wondering if I could use these to describe the same.

"The materials she sent us are quite voluminous. The document has 21 pages of a single-spaced text."

"The exam is very wide-ranging/ comprehensive."

2)" I think that some countries lag behind us when it comes to being open to change."

Could 'lag behind' be used in a conversation?

Thank you.