Prefix -un and suffix -ness

When someone is ill, that person has an ...

I like quite rooms. So ... is very important to me.

This state makes you feel happy.

I am writing a sad story. It's main topic is ...

This condition is good because you can see your things tidy.

When we use the prefix -un in a word like "happy", are we changing the word category or does it continue being an adjective?

I am very bad at playing sports. I am weak. That's my ...

They never smile or say hello. They're very ...(not friendly).

The word "unfriendly" means not ...?

My room is a mess, it isn't tidy. It's ...

When we add the suffix -ness to a word like happy, we have a new word category. Is it an adjective, a noun or a verb?

The opposite of helpful is...

The game hasn't got fair rules. It is ...

She listens to everyone's problems. She expresses her k...