What does this text mean?

We should fulfill our duty.

This is the busiest time up to this very moment.

The greater part of the time is spent on work.

I am working now.

I see, that's very interesting.

Yui is my best friend.

He taught me how to tie a tie.

The troposphere is the lowest part of the Earth's atmosphere, and most of the weather occurs here.

My son has started learning taekwondo.