Above all, grammar is the most important in learning Japanese.

We need personnel who can handle any problem.

What is your name?

Let's see, what is this?

He said nothing.

Have you decided which movie to watch?

It's better for him not to know the truth. After all, ignorance is bliss.

He is feigning ignorance about that problem.

He knows that pain through his own experience.

I have no way of knowing what he is thinking.