It's difficult to understand his explanation.

My understanding of this issue has deepened.

We need to deepen our understanding of this issue.

It's difficult to understand his explanation.

Can you answer this question?

His explanation was impossible to understand.

A new approach is needed to solve this set of problems.

The main problem with this project is the lack of communication.

This question text is too difficult, it's hard to understand.

This exam is a matter of life or death for me.